有機金屬氣相磊晶法低溫砷化鎵的變溫霍爾量測及深能階暫態能譜量測

Abstract

本文是以變溫霍爾量測及深能階暫態能譜量測法來探討有機金屬氣相磊晶 法低溫砷化鎵的一些性質.利用變溫霍爾量測,可以得到深,淺能階的缺陷 濃度,活化能.當磊晶溫度為500C時,以TEGa,TBAs為反應分子源成長的樣 品,以變溫霍爾量測得到的深能階缺陷的活化能為0.485eV,而缺陷濃度 是3.25*10^15(cm^-3).以深能階暫態能譜量測低溫深化鎵,發現了兩個主 要缺陷,分別為氧缺陷及EL2.不管使用的砷分子源為TBAs或AsH3,可以發現 氧缺陷在V/III變小時,其濃度會增加.而EL2的濃度在500C時,會比其它較 高的溫度下來的大,我們推究此現象是由於在較低溫度時,存在較多量的鎵 空缺造成的. We use Temperature Dependence Hall (TDH)measurement and Deep Level Transient Spectroscopy(DLTS) measurement to investigate t- he properties of the low temperature(~500℃) MOCVD GaAs films(LT -GaAs). Using TDH measurement,we can find the concentration and act- ivation energy of the deep level trap。A sample grown at 500℃， using TEGa and TBAs as source precursors ,It is find that the h- igh concentration 3.25×1015 cm-3,trap center located at 0.485 eV below conduction band has a dramatic influence on the electr- ical properties of LT-GaAs samples. In DLTS measurement ,two deep level traps ,peaked at ~0.55 eV and ~0.8 eV below conduction band ,are observed in LT- GaAs s- amples. They are identified as oxygen trap and EL2 trap respect- ively. It is found that the concentration of oxygen trap became larger as the V/III ratio is decreased, no matter of TBAs or As- H3 being used. On the other hand ,the occurrence of EL2 is very sensitive to the growth temperature .The concentration become l- arger at low temperature .We believed that such phenomenon is m- ainly caused by the shortage of reactive Ga atom on the growing surface, resulted from a low temperature growth environment.