Analysis of Experiments - Lab Report Example

LAB WORK No I(V) Characteristics of a Schottky Diode Contents I(V) Characteristics of a Schottky Diode i Contents ii Introduction and Theory iii Aims and Objectives iv Equipment iv Methodology v Results and Calculations vi vii viii ix x xi Measurements of C(V) characteristics of MIS structures xii Contents xiii Introduction and Theory xiv MIS-Structures xiv MOS-Structures xiv Aims and Objectives xv Equipment xv Methodology xv Results xvi Conclusion xviii Contents xx Introduction and Theory xxi Aims and Objectives xxii Equipment xxii Methodology xxii Conclusion xxv References xxv Jeff Tyson 2009, How LCDs Work, accessed on 28th February 2013 at http://electronics.howstuffworks.com/lcd2.htm xxvi Contents 28 Introduction and Theory 29 Future Prospects of Solar Cell Development 31 Aims and Objectives 31 Equipment 32 Methodology 32 Results and Calculations 32 Bibliography 36 Introduction and Theory In this laboratory experiment, the principles and operations of the Schottky diode become analysed. These diodes are extensively utilised in the following applications: Voltage clamping – occurring through voltage drops in forward bias and high density of current. Reverse Voltage Discharge Protection: utilised in preventing solar cells from during the night through the solar panels. Rectifiers in switch-mode power supplies: owing to the forward voltage and short recovery time. The Schottky diode is formed through the creation of contact between a metal contact (anode) and a semiconductor (cathode). These diodes differ from other standard (PN junction) devices because of the rectification that occurs between the metal contact and the semiconductor. This is performed because the work function remains different from that of the "non-uniform" doping profile. The conduction in a Schottky is not controlled by minority carrier recombining with a semiconductor, but by thermionic emissions of carriers over the barrier between the anode and cathode. Because of the fact that it is not controlled by the minority carriers, the switching speed of the device becomes independent of the minor carrier effects. The most common metals used in the manufacturing processes for Schottky diodes are platinum, titanium or gold. The diagrams show the Schottky junction in its two separate biasing modes. The top band diagram (a) is forward bias and (b) is reverse bias. Because of the bias applied to the junction, the junction is no longer in equilibrium. This makes it necessary for the Fermi levels to stay constant throughout the diode. This makes it possible the Fermi levels to move with the voltage that is applied to the circuit. The offset from their equilibrium position equals to qV, where V is the applied voltage. The voltage across the junction therefore becomes fbi -V. The expression for electric field E (x), maximum electric field Emax, depletion region d, and charge QJ remain valid for the biased diode as long as the potential fbi -V. (Information about the Fermi Levels of the Schottky diode was found using this PDF http://www.hit.ac.il/staff/vagner/Schottky.PDF. Unfortunately is does not state author or publisher ) Aims and Objectives The aims and objectives for this experiment remains seeking further understanding of the Schottky diodes and assist in determining the ideality factors of these diodes. Equipment The following equipment shall be utilised for the purposes of this experiment Schottky Diode a sample of MS contact DC power supply AVO (Ammeter) DVM (Voltmeter) Resister 1KΩ (1/2W) Methodology 1) Connect the Schottky diode to the circuit according to diagram (a), ensuring the markings on the physical device align with those shown on the diagram. (Ensure the DC power supply is set to give zero voltage before switching it on.) 2) Switch the power supply on and increase the applied voltage in small steps making recordings at each step. 3) Repeat the same measurements using the circuit shown in diagram (b). 4) Plot the diode current against the applied voltage for both polarities. 5) Repeat the measurements and calculation in (1-4) for a sample of metal-semiconductor (MS) structure Results and Calculations Below are the results taken from the AVO and DVM for the Schottky diode in forward and reverse bias and graphical representations of the results. Schottky Diode FWD Bias Vin (V) Voltage Out (V) AVO (mA) Logarith of Current 0.1 0.09 0.0113 -4.482952553 0.2 0.136 0.0653 -2.728763243 0.3 0.157 0.144 -1.937941979 0.4 0.169 0.233 -1.456716825 0.5 0.178 0.3245 -1.125469743 0.6 0.184 0.41 -0.891598119 0.7 0.19 0.511 -0.671385689 0.8 0.194 0.606 -0.500875293 0.9 0.198 0.7 -0.356674944 1 0.202 0.798 -0.225646682 1.5 0.214 1.283 0.249201086 2 0.223 1.773 0.572673027 2.5 0.229 2.266 0.818016163 3 0.234 2.75 1.011600912 3.5 0.238 3.24 1.17557333 4 0.242 3.73 1.316408234 4.5 0.245 4.22 1.439835128 5 0.248 4.71 1.549687908 6 0.253 5.66 1.733423892 7 0.257 6.68 1.899117988 Schottky Diode REV Bias Voltage In (V) DVM (V) AVO (nA) Logarith of Current 0.1 0.102 0.5 -7.60090246 0.2 0.202 0.5 -7.60090246 0.3 0.302 0.5 -7.60090246 0.4 0.402 0.5 -7.60090246 0.5 0.502 0.5 -7.60090246 0.6 0.602 0.5 -7.60090246 0.7 0.702 0.5 -7.60090246 0.8 0.802 0.6 -7.418580903 0.9 0.902 0.6 -7.418580903 1 1.002 0.6 -7.418580903 1.5 1.502 0.7 -7.264430223 2 2.002 0.8 -7.13089883 2.5 2.502 0.8 -7.13089883 3 3.002 0.9 -7.013115795 3.5 3.503 1 -6.907755279 4 4.003 1.1 -6.812445099 4.5 4.503 1.2 -6.725433722 5 5.004 1.2 -6.725433722 6 6.003 1.4 -6.571283042 7 7.004 1.5 -6.502290171 Ideality factor 1.047 Below are the results taken from the AVO and DVM for the MS Structure in forward and reverse bias and graphical representations of the results. MS Structure FWD Bias Voltage In (V) DVM (V) AVO (mA) Log of Current 0.1 0.102 0.0001 -9.210340372 0.2 0.202 0.0002 -8.517193191 0.3 0.302 0.0003 -8.111728083 0.4 0.402 0.0008 -7.13089883 0.5 0.501 0.001 -6.907755279 0.6 0.598 0.004 -5.521460918 0.7 0.7 0.003 -5.80914299 0.8 0.796 0.007 -4.96184513 0.9 0.865 0.036 -3.324236341 1 0.942 0.058 -2.847312268 1.5 1.273 0.298 -1.210661792 2 1.536 0.443 -0.814185509 2.5 1.753 0.706 -0.348140041 3 1.958 0.997 -0.003004509 3.5 2.14 1.3 0.262364264 4 2.39 1.63 0.488580015 4.5 2.44 1.95 0.667829373 5 2.61 2.26 0.815364813 6 2.86 2.93 1.075002423 7 3.16 3.63 1.289232648 MS Structure REV Bias Voltage In (V) DVM (V) AVO (nA) 0.1 0.102 0.1 0.2 0.202 0.1 0.3 0.302 0.1 0.4 0.402 0.1 0.5 0.502 0.1 0.6 0.602 0.1 0.7 0.703 0.1 0.8 0.803 0.1 0.9 0.902 0.1 1 1.003 0.1 1.5 1.503 0.2 2 2.003 0.2 2.5 2.503 0.3 3 3.003 0.3 3.5 3.503 0.4 4 4.004 0.5 4.5 4.054 0.6 5 5.004 0.7 6 6.004 1.1 7 7.004 1.3 Ideality Factor 112 LAB WORK No 2: Measurements of C(V) characteristics of MIS structures Contents I(V) Characteristics of a Schottky Diode i Contents ii Introduction and Theory iii Aims and Objectives iv Equipment iv Methodology v Results and Calculations vi vii viii ix x xi Measurements of C(V) characteristics of MIS structures xii Contents xiii Introduction and Theory xiv MIS-Structures xiv MOS-Structures xiv Aims and Objectives xv Equipment xv Methodology xv Results xvi Conclusion xviii Contents xx Introduction and Theory xxi Aims and Objectives xxii Equipment xxii Methodology xxii Conclusion xxv References xxv Jeff Tyson 2009, How LCDs Work, accessed on 28th February 2013 at http://electronics.howstuffworks.com/lcd2.htm xxvi Contents 28 Introduction and Theory 29 Future Prospects of Solar Cell Development 31 Aims and Objectives 31 Equipment 32 Methodology 32 Results and Calculations 32 Bibliography 36 Introduction and Theory In this experiment, MOS-structured materials will be through a probe and LCR meter to establish the CV characteristics present in the material. MIS-Structures A MIS-Structured capacitor consists of three layers of metal, insulating material and semi-conductor material. The capacitor name comes from these materials Metal Insulator Semiconductor MIS MOS-Structures A MOS- Structured capacitor consists of a semiconductor substrate with a thin layer and a metal contact and is made up using a Metal-Oxide-Semiconductor. The semiconductor substrate is known as the “gate” and the metal contact is called the “bulk contact”. (Zeghbroeck, 2011) The diagram below shows the MOS structure layout and how the experiment will be displayed Probe on metal plate This is the set-up of the experiment that is to be carried out. Here the MOS-Structured material can be seen (on left) connected to the LCR Meter via a Probe. Figure 1 the MOS structure Aims and Objectives The aims and objectives of the experiment are to understand the various features and characteristics of the MIS structure while determining the parameters of the MOS structure Equipment The following equipment shall be utilised within the experiment 1. Sample of MOS-Structure 2. LCR Bridge - Wayne Kerr 4225 3. Adapter 4. Power Supply Methodology 1. Connect the LCR meter to the power supply (as shown in the above diagram) making sure that the positive voltage is applied to the + port on the LCR Meter. NB: (DO NOT CHANGE THE CONNECTION TO THE POWER SUPPLY! The polarity on the sample can be changed by swapping the wires (a) and (b). 2. Take the MOS-Structure and place it on the metal plate (as shown above). 3. Place the probe on one of the metal circular electrodes on the MOS-Structure. 4. The probe and the metal plate are then connected to the LCR Meter port via the wires (a) and (b). 5. Set the LCR Meter to the capacitance option and set frequency to 120 Hz. 6. Measure the capacitance of the meter at a different bias voltage in a range of ± 5 V (step of 0.5 V). 7. Repeat step 6. but change the frequency in step 5. to 1 KHz and then 10 KHz. 8. Plot the results all on the same graph so that C-V characteristics at the different frequencies can be compared. 9. Using the results, calculate Ci, CFB and di and using the graph find VFB and calculate the value of density of surface states (Nss). Results The following results table shows the capacitance at the three different frequencies when voltage is changed from ±5 V (step of 0.5V). Capacitance at frequency Capacitance at frequency Capacitance at frequency Voltage (V) (nf) at 100/120 Hz (nf) at 1KHz (nf) at 10KHz 0 2.8 2.78 2.78 -0.5 2.778 2.773 2.768 -1 2.764 2.755 2.7499 -1.5 2.746 2.727 2.721 -2 2.675 2.675 2.669 -2.5 2.564 2.569 2.563 -3 2.379 2.363 2.354 -3.5 2.143 2.106 2.012 -4 1.868 1.413 1.0148 -4.5 1.9 0.766 0.54 -5 1.367 0.673 0.505 This graph shows the CV curve at the three different frequencies. This graph shows the CV curve at the three different frequencies. Below the calculations can be seen that were calculated from the results table and graph. Firstly Ci, CFB and di were calculated using the formula: Then VFB and Nss were calculated using the formula: Conclusion The graph is far away from an ideal set of readings, this is due to current leakage on the device the type of Si used is ntype (question 9) on sheet Bibliography Texes, U. o. (2010, 10 10). Interconnect and Packaging Research group. Retrieved 11 29, 2012, from http://www.me.utexas.edu/~ho/facilities.htm Zeghbroeck, B. V. (2011). Principles of Semiconductor Devices. Retrieved 11 29, 2012, from ecee.colorado.edu: http://ecee.colorado.edu/~bart/book/book/chapter6/ch6_2.htm LAB WORK No 4: Characterization of LED Contents I(V) Characteristics of a Schottky Diode i Contents ii Introduction and Theory iii Aims and Objectives iv Equipment iv Methodology v Results and Calculations vi vii viii ix x xi Measurements of C(V) characteristics of MIS structures xii Contents xiii Introduction and Theory xiv MIS-Structures xiv MOS-Structures xiv Aims and Objectives xv Equipment xv Methodology xv Results xvi Conclusion xviii Contents xx Introduction and Theory xxi Aims and Objectives xxii Equipment xxii Methodology xxii Conclusion xxv References xxv Jeff Tyson 2009, How LCDs Work, accessed on 28th February 2013 at http://electronics.howstuffworks.com/lcd2.htm xxvi Contents 28 Introduction and Theory 29 Future Prospects of Solar Cell Development 31 Aims and Objectives 31 Equipment 32 Methodology 32 Results and Calculations 32 Bibliography 36 Introduction and Theory The laboratory experiment looks at the functioning of different coloured LED and the effect of energy on determining the colour of the LED A Light-Emitting Diode can be defined as a semiconductor source of light, operating with a diode installed in a forward bias. Upon switching the device the electron and electron holes combine and produce light. The colour of the produced light becomes determined by the energy applied to the band-gap of the semiconductor. The device can be utilised in the following applications Lasers Car Lights Traffic Lights Smart lighting (can be used to transmit broadband data) Movement Sensors (computer mice) The easy and quick modulation of LEDs remains the reason behind their extensive application in optical fibre. The materials utilised in the LED remain fundamental determinant of the colour produced when the device is lit. This is normally affected by the band-gap, with a wide gap resulting in shorter wavelengths and vice-versa. The diagram below shows an LED producing a range of colours (micro.rohm 1997) Figure 2 a LED with different colours Aims and Objectives The aims and objectives of this laboratory experiment are to study various characteristics of LEDs including the light intensity and voltage characteristics. Equipment The following equipment with be utilised within the experiement: Three LEDs (1 x red, 1x yellow, 1 x green) Optical spectrum analyser RSO 6000 DC power supply Digital Multimeter 1 x 470 kΩ resistor Methodology Connect red LED diode to the circuit according to the diagram below. Ensure the markings on the device align with the diagram below. Figure 3 LED connection 2) Arrange the optic fibre to collect the light from the LED 3) Switch the Spectrum Analyser on 4) switch on the power supply and record the voltage and current. Increase the power supply and repeat the step severally. Use the results from these tests to plot a graph of current – voltage. 5) Record the emission spectra of LED at any three different voltages and save the data as ASCI file. 6) perform steps 4 and 5 for all the three LED present in the experiment 7) Plot the spectra of all three LEDs. From the wavelength values of the spectral maxima calculate the respective values of the energy band-gap for semiconductor materials used. Results Green LED Voltage (V) Voltage Across Diode(V) Current(mA) 5 2.04 6.94 4.5 2 4.86 4 1.99 2.84 3.5 1.95 1.06 3 1.92 0.15 2.5 1.88 0.01 2 1.81 0.0007 1.5 1.5 0 1 1 0 0.5 0.5 0 0 0 0 these are the wavelengths of the spectra Energy band gaps of the semi conductors using formula from lab sheet Blue LEDpeak (i) = E (ev) = 1242.4 / 870nm = 1.42 This can be Gallium arsenide Blue LED peak(ii) = E (ev) = 1242.4 / 1056nm=1.17 This can beCopper(II) oxide Green LED peak(i) = E (ev) = 1242.4 / 1366nm=0.909 This can beSilver sulfide Green LED peak(ii) = E (ev) = 1242.4 / 1389nm=0.89 This can beSilver sulfide Red LED = E (ev) = 1242.4 / 1735nm = 0.716This can beGallium antimonide Conclusion Red and Green LED’s have higher current across them but the green Led can have a much larger voltage across it. The current recording from the lowest to the highest would be as follows blue, red and green References Mark Davison 1997, Strain Gauges and the Wheatstone Bridge ,accessed on 29th February 2013 at http://media.paisley.ac.uk/~davison/labpage/gauges/gauges.html Jeff Tyson 2009, How LCDs Work, accessed on 28th February 2013 at http://electronics.howstuffworks.com/lcd2.htm Author N/A,Portable ,luggage scale, accessed on 25th February 2013 at http://www.xy-scale.com/en/productshow.asp?productid=783&catalogid=129&type_id=0 LAB WORK No 5: Characteristics of a solar cell Contents I(V) Characteristics of a Schottky Diode i Contents ii Introduction and Theory iii Aims and Objectives iv Equipment iv Methodology v Results and Calculations vi vii viii ix x xi Measurements of C(V) characteristics of MIS structures xii Contents xiii Introduction and Theory xiv MIS-Structures xiv MOS-Structures xiv Aims and Objectives xv Equipment xv Methodology xv Results xvi Conclusion xviii Contents xx Introduction and Theory xxi Aims and Objectives xxii Equipment xxii Methodology xxii Conclusion xxv References xxv Jeff Tyson 2009, How LCDs Work, accessed on 28th February 2013 at http://electronics.howstuffworks.com/lcd2.htm xxvi Contents 28 Introduction and Theory 29 Future Prospects of Solar Cell Development 31 Aims and Objectives 31 Equipment 32 Methodology 32 Results and Calculations 32 Bibliography 36 Introduction and Theory Figure 4circuit diagram (University, 1997) Figure 5 a typical solar cell The above diagram indicates a crystalline structure of a typical solar cell. The front and rear contacts of the cell extract the electric current generated by the semi-conductor in the cell. The cells top structure consists of widely spaced, thin metal strips. The positioning of these strips allows light in between the strips, which is absorbed and converted to electric current. The strips then transfer the current to the bas bar. The cell is coated with dielectric material which serves the purpose of minimising reflection of light from atop the cell. The Photovoltaic Effect: Figure 6 how PV cells create electricity from solar power Absorbing light into the cell Breaking the bond and transferring the electrons between different bands. Space in the cell becomes freed and electrons and hole begin moving in opposite directions. metal contacts are used to create a circuit. Future Prospects of Solar Cell Development Solar panels expose a lot of energy to wastage as they manage to only convert about 20% of the light they are exposed to. Further development should be encouraged to increase the rate of conversion, and consequently reducing wastage of solar power. Thin film PV panels seek to provide a solution to the extreme wastage experienced in the rigid panels. Their flexibility enables them to gain a wider coverage making them more effective. . Aims and Objectives In undertaking this laboratory research, the ideality factor of diodes will be determined, in seeking to understand the functioning of a solar cell. The report also seeks to provide insight into the fabrication of these cell and the future prospects for development of solar cells. Equipment 1. Solar Cell 2. Xenon White Light Source 3. 2x DVAM (one for ammeter one for voltmeter) 4. Variable Resister 5. Light Power Meter Methodology 1. construct the circuit 2. Switch on the light source (to measure load characteristics of solar cell) vary the resister from 10Ω to 1MΩ and record values on the two DVAM 3. Replace the solar cell with a light power meter and measure the power of incident light (P.I.L.) per mm­2 4. Present the results in graphs and make all essential calculations Results and Calculations Table 1 measurements (including calculated FF) Resistance (Ω) Voltage (V) Current (A) Power (mW) F.F 10 0.04 0.004015 0.0001606 0.02008 20 0.0789 0.004009 0.00031631 0.03954 50 0.1998 0.004012 0.000801598 0.1002 100 0.396 0.004015 0.00158994 0.19874 200 0.81 0.003995 0.00323595 0.40449 500 1.61 0.003198 0.00514878 0.6436 1000 1.846 0.001853 0.003420638 0.42758 2000 1.933 0.0009714 0.001877716 0.23471 5000 1.98 0.0003975 0.00078705 0.09838 10000 1.9855 0.000199 0.000395115 0.04939 20000 1.9925 0.0000999 0.000199051 0.02488 50000 1.996 0.0000402 8.02392E-05 0.01003 100000 1.9972 0.0000203 4.05432E-05 0.00507 200000 1.998 0.0000102 2.03796E-05 0.00255 500000 1.9976 0.0000042 8.38992E-06 0.00105 1000000 1.9986 0.0000022 4.39692E-06 0.00055 Below are the graphs of the results that were taken in the lab F.F MAX = 0.643 Power Produced by solar cell (P.s.c) Power Max = 5.1mW Area = 420mm2 P.s.c = 5.1mW / 420mm2 = 0.012mm2 Power of Incident light (P.I.L) Power meter reading = 3.32mW Area = 33mm­2 3.32mW / 33mm2 = 0.1mm2 Efficiency = 0.012 / 0.1 = 12% Bibliography University, S. (1997). how solar cells work. Retrieved 12 18, 2012, from solar electricty: http://www.southampton.ac.uk/~solar/intro/tech6.htm Read More