Abstract
This paper reports the material characteristics of In0.66Ga0.34As/InyAl1-yAs high electron mobility transistor (HEMT). The linearly graded InyAl1-yAs buffer layer was grown on InP substrates by gas source molecular beam epitaxy (GSMBE). The influence of InyAl1-yAs graded buffer layer with different thickness and different indium contents on the surface quality, the electron mobility and the concentrations of two-dimensional electron gas (2DEG) was studied. It was found that the electron mobility and concentration at 300 K (77 K) were 8570 c
HEMT is an important solid-state device for millimeter-wave and terahertz-wave application. InP based InxGa1-xAs/InyAl1-yAs PHEMT has attracted more and more attention due to its excellent high frequency and low noise coefficient properties, which can be widely used in the field of electronic devic
Increasing the indium contents of the InGaAs channel is one of the ways to improve the electron mobilit
In this paper, the influence of InyAl1-yAs graded buffer layer on the characteristics of InP-HEMT is systematically studied. Material properties of the InyAl1-yAs graded buffer layer are mainly investigated in different thickness and indium contents of InyAl1-yAs graded buffer layer.
The fluxes of group Ⅲ elements indium(In), gallium(Ga), aluminum(Al) were controlled by adjusting effusion cell temperatures, respectively. The silicon(Si) was used as n-type doping source and the groupⅤelements P2 and As2 were obtained by cracking phosphine and arsine at 1000℃.
InP substrate was pre-degassed at about 350 °C in the preparation chamber for 1 hour. Using P2 flux to protect substrate surface when the substrate temperature approaches to 300℃. The substrate temperature is approximately 425℃ for 3 minutes until the (4×2)-(100) In-stable reconstruction occurs. It uses situ reflected high energy electron diffraction (RHEED) to monitor substrate surface reconstructio
InP-HEMT structure illustrated in
The mobility and electron concentration was studied in different indium contents of InGaAs channel. The results of four different indium contents channel are shown in

Fig. 1 Hall mobility and electron concentrations in different channel indium contents
图1 不同沟道铟含量的霍尔迁移率和电子密度
According to the HRXRD image in

Fig. 2 HRXRD (004) ω-2θ scans for InAlAs graded buffer layer with different thickness
图2 不同厚度InAlAs渐变缓冲层的HRXRD (004) ω-2θ扫描曲线
The InAlAs graded buffer layer with different thickness and the InGaAs channel layer were grown. AFM tapping mode on 5 µm×5 µm area was used to characterize the surface morphology of these samples. As is shown in

Fig. 3 The surface morphology of the InAlAs graded buffer layer with different thickness
图3 不同厚度的InAlAs渐变缓冲层的表面形貌
The channel material quality plays a critical role in the HEMT performance. Therefore, In0.66Ga0.34As channel materials grown on different thickness of InAlAs graded buffer layer were studied.

Fig. 4 The surface morphology of the InGaAs channel with different InAlAs graded buffer layer thickness
图4 带不同厚度InAlAs渐变缓冲层的InGaAs的表面形貌
The mobility and electron concentration of InAlAs graded buffer layer with different thickness were characterized by HALL. Ultimately it can be found from the

Fig. 5 Hall mobility and electron concentrations in different InAlAs graded buffer layer thickness
图5 不同厚度InAlAs渐变缓冲层霍尔迁移率和电子密度
In order to more comprehensively characterize the effect of InAlAs graded buffer layer on material performance. The influence of different indium contents on material performance was investigated when InAlAs graded buffer layer thickness was 50 nm. The indium and aluminum contents of InyAl1-yAs were adjusted through the linear decreasing of aluminum source cell temperature. The results were shown in
The surface quality of 50 nm InAlAs graded buffer layer with different aluminum contents and In0.66Ga0.34As channel layer above InAlAs graded buffer layer were studied. The AFM images shown in

Fig. 6 The surface morphology of the InAlAs graded buffer layer with different aluminum contents
图6 不同铝含量的InAlAs渐变缓冲层的表面形貌

Fig. 7 The surface morphology of the InGaAs channel with different aluminum contents
图7 带不同铝含量InAlAs渐变缓冲层的InGaAs的表面形貌
In sample Al contents 48%→34% of

Fig. 8 TEM energy spectrum image of InP-HEMT with InAlAs graded buffer layer
图8 带InAlAs渐变缓冲层的InP-HEMT的TEM能图

Fig. 9 TEM Cross-sectional image of InP-HEMT with InAlAs graded buffer layer
图9 带InAlAs渐变缓冲层的InP-HEMT的TEM截面图
According to the

Fig. 10 Hall mobility and electron concentrations in different InAlAs graded buffer layer aluminum contents
图10 不同铝含量的InAlAs渐变缓冲层霍尔迁移率和电子密度
In this paper, the influence of different thickness and different indium contents of InyAl1-yAs graded buffer layer on the surface quality, the mobility and the concentrations of two-dimensional electron gas (2DEG) was demonstrated. It is found that the mobility and concentration at 300 K (77 K) were 8570 c
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