摘要

在本文中比較兩種不同銦成分通道層的AlGaAs/InGaAs 異質結構場效電晶體及摻雜對元件特性的影響。
我們利用超晶格式緩衝層來形成一個能障，使得電子不易注入至緩衝層，可以增進載子的限制力並改善元件的夾止及飽和特性。在高溫，元件也呈現良好的夾止及飽和特性。此外，我們利用摻雜載子提供層來增加通道中載子的濃度及提高元件的電流和異質轉導值。我們比較通道層中兩種不同銦成分的元件特性差別，由實驗結果得知通道中含較高的銦成分者有較大的載子移動性、異質轉導值及截止頻率。
我們利用濕蝕刻的方式來薄化蕭基層，因而有效地改善元件的特性。由實驗結果顯示較薄的蕭基層增進了元件的夾止特性並且提高了最大的異質轉導值。我們同時也探討了AlGaAs/InGaAs 異質結構場效電晶體的溫度特性。元件的電流及異質轉導值會隨著溫度上升而減少。我們也量測AlGaAs/InGaAs 異質結構場效電晶體的高頻、功率、雜訊特性。

Abstract

In this thesis, AlGaAs/InGaAs field-effect transistors using different indium content are fabricated. Furthermore, the -doped layer effect on the device characteristics has been studied.
A superlattice buffer inserted between channel and substrate for preventing electrons inject into substrate, resulting in improving carrier confinement in the channel and improving saturation and pinch-off characteristics, is studied. At high temperature, good saturation and pinch-off characteristics are observed. In addition, we use delta-doped supply carrier layer to enhance carrier concentration in the channel and to increase current density and extrinsic transconductance. The experimental results show higher carrier mobility, extrinsic transconductance, and cut-off frequency can be obtained by using higher indium composition.
By using wet etching of the Schottky layer, the device breakdown characteristics can be observed. The results show that the thin Schottky layer can improve the pinch-off characteristic and extrinsic transconductance obviously. The temperature-dependent characteristics of AlGaAs/InGaAs heterostructure field-effect transistors have also been studied. The current density and extrinsic transconductance decrease with increasing temperature.We also measure microwave, power, and noise characteristics of AlGaAs/InGaAs heterostructure field-effect transistors.

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