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Very high performance InGaP/InGaAs/GaAs PHEMTs will be demonstrated. The fabricated InGaP gated PHEMTs devices with 0.25 160 m 2 and 0.25 300 m 2 of gate dimensions show 304 mA/mm and 330 mA/mm of saturation drain current at GS = 0 V, DS = 2 V, and 320 mS/mm and 302 mS/mm of extrinsic transconductances, respectively. Noise figures for 160 m and 300 m gate-width devices at 12 GHz are measured to be 0.46 dB with a 13 dB associated gain and 0.49 dB with a 12.85 dB associated gain, respectively. With such a high gain and low noise, the drain-to-gate breakdown voltage can be larger than 11 V. Standard deviation in the threshold voltage of 22 mV for 160 m gate-width devices across a 4-in wafer can be achieved using a highly selective wet recess etching process. Good thermal stability of these InGaP gated PHEMTs is also presented.

Vcs= -1.5 V to 0.3 V in 0.3 V step Stress@Vv,= 6v, vGS= o v -before stress --stresstor6Ominr . . -stressfor18Omins Abstract This work presents a study on the high reliability of noise characteristics of InGaP low noise PHEMTs, which was demonstrated through DC and thermal stress. The devices that we used were I n~.~~G a~.~~P / l n~.~~G a~.~~ As/GaAs low noise pseudomorphic high electron mobility transistors (PHEMTs) with the gate dimensions of 0.25 ~1 6 0 ,urn2. The DC-stress conditions are I ) VDs = 6V, V& = OV and 2) IG = -8 m4 (SOmA/mm). The ranging of thermal-stress is from IO0 "c to 250 "c. The noise characteristics were measured at 12 GHz and DC bias condition is VDs = 2 V, IDS = I O mA.The key noise-effect parameters of devices are the deep-trap behaviour in device, source/gate resistances, gate to source capacitance and intrinsic transconductance. We showed the very small variation of minimum noisefigure, NF,, and associated power gain, G, after DC and thermal stress by explaining the variation of these key parameters to demonstrate the high reliability in InGaP low noise PHEMTs.

An analytical model for super low-noise InAlAs/InGaAs/InAlAs/InPHEMTs is presented. The carriers are well confined in the quantum well formed in InGaAs due to the large conduction band discontinuities (AEC) at the InAlAsnnGaAs and InGaAsLnAIAs heterointerfaces. Moreover, a smaller electron effective mass in InGaAs results in a higher device transconductance g, and lower noise figure NF. The noise figure of InP based HEMTs is much lower than that of GaAs based pseudomorphic or normal HEMTs. The present model is based on a self-consistent solution of Schroedinger and Poisson's equations to calculate the properties of the quantum well formed in InGaAs, namely the average distance of two-dimensional electron gas (2DEG), x, , , and the position of Fermi level, EF, as a function of 2DEG concentration n,. Instead of using a two-line o r a n exponential approximation, an improved velocity electric field (vd-E) characteristic is used to calculate the current-voltage (I-V) characteristics, small-signal parameters and noise performance analytically. Based on the model developed by Liu and Anwar et al. (1, 21, g, is calculated and the result shows an excellent agreement with experimental data. The present model yields a minimum noise figure, Fmin, of 0.8 and 1.2 dB a t 60 and 94 GHz, respectively, which well fit to the experimental data [3]. The noise performance of this class of devices with different gate lengths is studied in the present model. A-IntroductionIn the past several years, the superior electron transport properties, namely high electron mobility and saturation velocity, in the InGaAs channel as compared to those of the conventional AlGaAsIGaAs and pseudomorphic AlGaAsIInGaAslGaAs HEMTs have been demonstrated by several researchers [ 1-81. A higher conduction band discontinuity AEc between InAlAs and InGaAs, a smaller electron effective mass of channel material, the lattice-matched to InP substrate result in a better two-dimensional electron gas (2DEG) carrier confinement in the channel, a higher transconductance g, and the super 0-7803-31 79-6/96 $5.00 01996 IEEE 365

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