Distribution of the Main Electron Trap EL2 in Undoped LEC GaAs

The main electron trap EL2 is thought to be responsible for the semi-insulating nature of an undoped LEC GaAs for IC's. Distribution of this electron trap has been measured in this study by a normal DLTS method. It was found that the trap density of EL2 was as high as 3–5 ×1016 cm-3 taking into account the non-ionized front region of the depletion layer. Concentration of EL2 sometimes fluctuates by a factor of 2–3 within a wafer as well as from wafer to wafer. There was no dependence of EL2 density on etch pit density (EPD), however, when EPD was less than 2×105 cm-2. For samples with EPD above 2×105 cm-2, EL2 density increased slowly with an increase of EPD.