應用於高頻低雜訊具有砷化銦鎵/砷化銦 超晶格通道之變質型高速電子遷移率電晶體(MHEMT)之研究

Abstract

本次研究中探討使用砷化銦鎵/砷化銦 超晶格為通道層之InAlAs/InGaAs變質型高電子遷移率電晶體(MHEMTs)在高頻的應用。

利用砷化銦鎵/砷化銦超晶格通道在變質型砷化鎵基板上能夠有效提升通道層的銦含量。此外在超晶格結構中，由於電子減少與通道中銦原子或鎵原子的不規則散射，因而擁有比傳統砷化銦鎵通道較好的電子傳輸性質。此外砷化銦的能階較低，通道中的較多電子會被限制在砷化銦量子井中，使得整個元件的電子傳輸特性將以砷化銦為主，因此能夠有效提升使用超晶格通道之變質型高電子遷移率電晶體的電子特性

在元件特性方面，使用超晶格通道之變異型100 nm高電子遷移率電晶體其在此次的研究中其汲極飽和電流密度為476 mA/mm，而電流在0.9 V的汲極偏壓下最大的互導係數可達886 mS/mm。元件的電流增益截止頻率及最大共振頻率皆為170 GHz。雜訊方面，元件在16GHz 的頻率下，雜訊值為0.77 dB。

因此，本次研究成功的研發出在變質型砷化鎵基板上，利用超晶格結構，能有效提高通道層中的銦含量，並且應用此結構之元件具有優越的電流以及高頻低雜訊的特性。

In this dissertation, the feasibility of using (In0.53Ga0.47As)/(InAs) superlattice as the channel in the InAlAs/InGaAs metamorphic high electron mobility transistors (MHEMT) for high frequency applications is studied.

The indium content in the channel can effectively be increased by using the InGaAs/InAs superlattice structure on metamorphic GaAs substrate. In addition, because of the reduction of electron disorder scattering by composite In and Ga atoms in the channel, the electron transport properties in the superlattice structure are enhanced. Furthermore, more electrons are confined in the InAs quantum wells in the superlattice channel due to the low bandgap of InAs. Consequently, the performance of MHEMT with superlattice channel is improved.

In this study, the metamorphic HEMT with superlattice channel exhibit excellent performance such as IDSS of 476 mA/mm, gm of 886 mS/mm at drain bias voltage of 0.9V with gate length of 100 nm. The device also demonstrates a cutoff frequency fT of 170 GHz and a maximum frequency of oscillation fmax up to 170 GHz. The noise figure of the device is 0.77 dB at 16GHz.

Consequently, a high indium content superlattice channel HEMT on metamorphic GaAs substrate is successful developed, and the device exhibits superior DC and RF performance than conventional InGaAs metamorphic HEMT for high frequency application.