The effect of defects on InAs/AlSb/GaSb resonant interband tunneling diodes

Abstract

Defect phenomena, that impact on the uniformity of resonant interband tunneling diodes grown by molecular beam epitaxy (MBE), have been examined by current voltage (IV) measurements and atomic force microscopy (AFM). AFM topography measurements are found to be useful in determining the detailed structure of defects that range in size from one /spl mu/m in diameter and 0.3 /spl mu/m deep to much smaller. The peak to valley ratio (P/V) is a measure of the quality of a device, and a correlation has been found between devices with low P/V ratios and AFM measurements. Defects with a density of 10/sup 3/ cm/sup -2/ have been found in devices grown on both InAs and GaAs substrates. IV measurements on diodes containing these flaws have P/V ratios that are one half the P/V of devices without them. AFM measurements have also revealed smaller defect features with densities of 10/sup 5/ to 10/sup 6/ cm/sup -2/ for some growths on GaAs substrates. Because of the high density, many of the devices contain at least one defect resulting in a lower than expected average P/V ratio for the wafer. The ratio of the peak current for positive bias to that for negative bias (I/sub p+//I/sub p-/) is another useful measure of device quality as it is a measure of the symmetry of a device. I/sub p+//I/sub p-/ has been found to decrease as the substrate temperature during MBE growth is increased. This is consistent with Ga segregation from the GaSb well into the AlSb barrier grown on it resulting in an AlGaSb barrier with a reduced barrier height.