No abstract

No abstract

No abstract

No abstract

Planar InGaAs(P)/InP p-in photodiodes have been successfully fabricated by low-pressure metalorganic chemical vapor deposition (LP-MOCVD). High-quality and uniform epitaxial layers are obtained. It is noted that the InGaAs layer background concentration is as low as 4:5 Â 10 13 cm À3. The dark current is significantly reduced by using a wider-band-gap material of quaternary In x Ga 1Àx As y P 1Ày as a cap layer to reduce the device surface leakage current. In addition, the device becomes highly photosensitive due to the reduction of the absorption of the radiation in the narrow-band-gap In x Ga 1Àx As y P 1Ày cap layer. The p-in photodiode with a wide-band-gap InP cap layer exhibits a dark current as low as 60 pA at À10 V bias, corresponding to a dark current density of 4:2 Â 10 À7 A/cm 2 .

Growth of carbon doping Ga 0.47 In 0.53 As using CBr 4 by gas source molecular beam epitaxy for InP/InGaAs heterojunction bipolar transistor applications An n-p-n InGaP/GaAs heterojunction bipolar transistor ͑HBT͒ using a graded base doping profile has been fabricated by low pressure metalorganic chemical vapor deposition. A current gain of 77 and a base sheet resistance of 251 ⍀/sq are achieved in the graded-base HBT. Compared to the graded-base structure, the nongraded-base structure has a lower current gain ͑68͒ and a higher base sheet resistance ͑294 ⍀/sq͒. Furthermore, the studied graded-base HBT device also shows better microwave characteristics. The measured unity current-gain cutoff frequency ( f T ) can be improved from 18 to 22 GHz. The functional dependences of current gain, base sheet resistance, and microwave characteristics on the base doping profile are attributed to the graded-doping enhanced built-in field across the base and higher base doping at the emitter edge.

No abstract

A δ-doped In0.45Al0.55As/InGaAs metamorphic high-electron-mobility transistor (MHEMT) using an In0.45Ga0.55As/In0.65Ga0.35As inverse composite channel has been fabricated successfully and demonstrated. The inverse composite channel significantly reduces Coulomb scattering and consequently improves electron mobility as well as carrier confinement. Experimentally, a high extrinsic transconductance of 321 mS/mm and a drain–source saturation current density of 342 mA/mm are obtained for a 0.65 ×200 µm2 gate at 300 K. Meanwhile, degradation of the studied device, in terms of parameters such as G m,max, I DSS, and V th, with increasing temperature is not evident. A positive temperature coefficient of V th is observed. The measured f T and f max for a 0.65-µm-gate device are 41.6 and 53 GHz, respectively. In addition, the studied device also shows good microwave performances in a flat and wide operation region. From V GS = -2.5 to 0.5 V, the values of f T and f max are still over 33 GHz.