Review - Research Paper Example

d the design, the InAlAs-InGaAs-lnP lattice matched epitaxial layers were developed by the organo metallic vapor phae epitaxy on the lnP:Fe substrate. The layer structure consisted of 25nm lnP:Fe buffer layer, a 50nm ln(Ga,AL) graded layer, 300-nm n+ -InP:Si (6 10 cm ohmic contact layer and a 50-nm InAlAs Schottky-barrier enhancement layer. The graded layer was incorporated into the structure to remove conduction and valence band discontinuities that tend to degrade the high frequency performance citric acid:H202 was used to achieve an anisotropic mesa etch (Wohlmuth, Seo, Fay, Caneau, &.

Adesida, 2). The etch profile enabled a Ti: Au interconnection between the top ITO Schotty contact and the microwave probe pads. RF magnetron was used to deposit the ITO film (thickness 320nm, refractive index of 2.05) sputtering in the argon environment. The experimental results showed that the device had a low knee voltage of about 0.39v, which is in accordance to the background doping concentration of 4x1014 cm-3 (Wohlmuth et al, 2). The responsive of the devices was between 0.55-0.60 A/W at wavelength of 1.

31 mm and 0.563-0.583 for 1.55 mm at a bias of 5V. The dark current density of the Schottky contact increased as the diameter of the devices was reduced. This implied that the dark current of the devices is due to the surface-state conduction on the edges of the mesa rather than across the barrier contact (Wohlmuth, Seo, Fay, Caneau, &. Adesida, 3). At 100 mm, the lowest dark current was exhibited at 8.87x10-5 A/cm-2 at a bias of 5V. The frequency of the device was determined using the HP83420A light wave test set of wavelength 1.

55 mm, 50ohm characteristic impedance. The 3-dB cutoff frequency at 10V for 11, 50, 25, 20, 15 diameter devices was found to be 2.5, 10.3, 21.2, 23.7, 25GHZ respectively. The high responsiveness was up to 0.60A/W for 1.31 light and 0.583 A/W for 1.55 mm (Wohlmuth, Seo, Fay, Caneau, &. Adesida, 4). The paper aimed at investigating the