Improved Low-Frequency Noise and Microwave Performance of Enhancement-Mode InGaP/InGaAs PHEMT with a Liquid-Phase Oxidized GaAs without a Gate Recess

Abstract

This paper demonstrates an enhancement-mode InGaP/InGaAs metal-oxide-semiconductor pseudomorphic high-electron-mobility transistor (PHEMT) with a liquid-phase oxidized GaAs gate without a gate recess. Without a gate recess, the gate insulator is obtained directly by oxidizing the GaAs capping layer in the LPO growth solution, and fully planar surface is achieved around the active region. The proposed device shows a maximum transconductance of 141 mS/mm at V DS = 2 V and a maximum drain current density of 145 mA/mm at V GS = 2 V and V DS = 2 V. It also exhibits lower leakage current, improved subthreshold swing, suppressed low-frequency noise, and enhanced microwave performance than those of the referenced PHEMT.The advantages of using enhancement-mode (E-mode) pseudomorphic high-electron-mobility transistors (PHEMTs) as power devices for single supply operations have been recognized for some time. These advantages can facilitate circuit design and construction and render them less complex. They can also improve dc power consumption, efficiency, and operation time; 1 this has led to interest in applications for cellular phones. The buried gate approach 2,3 or double recess process 4,5 are commonly used techniques for high-performance E-mode PHEMTs. However, the gate-recess process creates more surface states that induce a gate leakage issue and generate parasitic capacitances that degrade device performance. Moreover, the Schottky barrier heights may still suffer from gate leakage issue. Suitable oxidation or passivation can satisfy dangling bonds, which reduce surface recombination centers and suppress carrier trapping within the surface states. In other words, using an oxide film to form a metaloxide-semiconductor (MOS) structure for metal-oxide-semiconductor pseudomorphic high-electron-mobility transistor (MOS-PHEMT) fabrication could improve the microwave characteristics and lowfrequency noise associated with the surface state and lattice scattering.Over the past years, a simple and selective liquid phase oxidation (LPO) on GaAs operated at low temperature (30-70 • C) has been proposed and investigated. 6 Previous works have reported the preliminary study of the dc performance, the pulse transient characteristics, 7 and RF performance 8 of the depletion-mode (Dmode) InGaP/InGaAs MOS-PHEMT. The pulse transient measurement shows much less impact of the surface trap effects for the D-mode MOS-PHEMT. However, the literature focuses less on the low-frequency noise and microwave characteristics of the E-mode InGaP/InGaAs MOS-PHEMT. 9 Low-frequency noise measurement is a commonly used method to investigate MOS interface properties of MOS-PHEMTs 10,11 and surface treatment properties of PHEMTs. 12,13 This paper presents a discussion on the low-frequency noise and microwave performance of an E-mode InGaP/InGaAs MOS-PHEMT with an oxidized GaAs gate without a gate recess to further understand the role of the gate insulator. Without a gate recess, the gate insulator is obtained directly by oxidizing the GaAs capping layer...

Reduced Subthreshold Characteristics and Flicker Noise of an AlGaAs/InGaAs PHEMT Using Liquid Phase Deposited TiO2 as a Gate Dielectric

“…As shown in Figure 7 (different samples from those shown in Figure 3 ), the measured unity-current-gain cutoff frequency ( f T ) and the maximum oscillation frequency ( f max ) were 17.3 (11.6) GHz and 26.4 (19.7) GHz at the maximum g m for the MOS-PHEMT (PHEMT). The trend is consistent with the results previously found for E-mode InGaP/InGaAs MOS-PHEMT with liquid phase oxidation (LPO) [ 26 ]. The increased microwave performances of the AlGaAs/InGaAs MOS-PHEMT may be attributed to the increase in the ratio of g m to gate-source capacitance ( C gs ).…”

“…The trend is consistent with the results previously found for E-mode InGaP/InGaAs MOS-PHEMT with liquid phase oxidation (LPO) [26]. The increased microwave performances of the AlGaAs/InGaAs MOS-PHEMT may be attributed to the increase in the ratio of g m to gate-source capacitance ( C gs ).…”

Decreasing Defect‐State Density of Al2O3/GaxIn1−xAs Device Interfaces with InOx Structures

“…An oxide/Ga x In 1− x As interface is frequently found as part of various device components (e.g., metal–oxide–semiconductor (MOS) high electron mobility transistor, structure, and IR detectors) currently used in electronics and in the design of many a potential future device (e.g., III–V MOS field‐effect transistor, and tunnel field‐effect transistor) . However, oxide/Ga x In 1− x As interfaces are usually considered as nonoptimized, adversely affecting the device performance: namely, they contain a high density of material defects that cause electronic defect states in the band‐gap area (gap states), which further increase the leakage current, nonradiative recombination, and Fermi‐level pinning, for example.…”