The Study of III-V Epitaxial Material on Si Substrates for High-Speed Electronic and Optoelectronic Applications
Edward Yi Chang
|關鍵字:||砷化鎵磊晶;高速元件;砷化鎵整合與矽基板上;矽鍺磊晶;GaAs on Si;HEMT;SiGe;Ge buffer|
在高速電子元件方面，我們成功的將砷化鋁鎵/砷化銦鎵通道的高速電子遷移率電晶體元件結構(AlGaAs/InGaAs channel HEMT) 透過矽鍺緩衝層，長在矽基版上面，其電子遷移率為3,550cm2/Vs，當在此晶片上製作完成ＨＥＭＴ元件後，在直流特性方面，當汲-源極電壓(VDS)1.5V時，在最大飽和電流(Idss)可以達到150mA/mm，轉導值(gm)可以達到155mS/mm，在偏壓為時14.2V，漏電電流為5□A。
In this dissertation, GexSi1-x metamorphic buffer layers were used for the growth of the III-V material on the Si substrate. Using Ge/GexSi1-x metamorphic structure as the buffer layer, the thermal expansion mismatch and the lattice mismatch problems of the interface between GaAs and Si was solved. The use of Si+ pre-ion-implantation combined with a GexSi1-x metamorphic buffer structure for the growth of the Ge layer on Si substrate was proposed. Enhanced strain relaxation of the GexSi1-x metamorphic buffer layer on Si substrate was achieved due to the introduction of point-defects by heavy dose Si+ ion-implantation. Because of both strain relaxation enhancement and the interface-blocking of the dislocations in the GexSi1-x metamorphic buffer structure, the total thickness of the buffer layer was only 1μm. The thinner buffer structures are preferred for the growth of the GaAs layers on Si substrate due to the large thermal expansion difference between these two materials. We demonstrated epitaxial growth of AlGaAs/InGaAs HEMT grown on Si substrate with Ge/GexSi1-x buffer is demonstrated for the first time in this study. The electron mobility in the In0.18Ga0.82As channel of the HEMT structure grown was 3,550cm2/Vs. After process, the HEMT device demonstrated a transconductance of 155 mS/mm and a saturation current of 150 mA/mm when the drain-source voltage (VDS) was 1.5V. After isolation etched, the HEMT structure demonstrated a leakage current of 0.016□A/□m when the bias voltage was up to 14.2V. A high mobility InAs channel MHEMT structure was also grown on Si substrate with 6o off angle toward to . The Hall measurement shows that the electron mobility of the InAs MHEMT grown on Si was 27,300 cm2/v-s. A novel Ge/GexSi1-x buffer layers were used as the buffer and were grown by using UHV/CVD method. The AlGaSb/AlSb/GaAs layers were grown by MBE process to accommodate the lattice strain induced by the large lattice mismatch of 7 % between the AlGaSb/InAs HEMT structure and the Ge layer. Self-assembled In0.22Ga0.78As quantum dots (QDs) on Si substrate by metal organic vapor phase (MOVPE) with Ge/SiGe as buffer layer grown were investigated. Transmission electron microscopy (TEM) and atomic force microscopy （AFM）images were used to observe the size and space distribution of the In0.22Ga0.78As QDs grown on the GaAs/Ge/GexSi1-x/Si layer structure. The influence of the growth temperature on the QDs size and density distribution was investigated. For QDs grown at 450℃, the density of the In0.22Ga0.78As dots was estimated to be 1×1011 cm－2 , the average size of In0.22Ga0.78As QDs were 20nm and PL spectrum was 110nm.
|Appears in Collections:||Thesis|