Deep levels in GaAs ultrashallow sidewall pin junctions measured by photocapacitance method

摘要

Photocapacitance measurements have been made on GaAs ultra-shallow sidewall p~+ i n~+ junctions, fabricated by low-temperature area-selective re-growth molecular layer epitaxy. Emission spectra were obtained of the photocapacitance, affected by the deep levels at the re-growth interface region. From the photocapacitance results, it is shown that the defect levels and their density differed, depending on the device sidewall mesa orientations, with the magnitude of deep level density increasing in the order of: normal mesa < 45°-inclined configuration < reverse mesa orientation. When photocapacitance results of sidewall p~+ i n~+ junctions were compared with current-voltage characteristics of sidewall p~+n~+ tunnel junctions, a good agreement was found. It is considered that the deep levels at the re-growth interface are a major factor controlling excess current in sidewall tunnel junctions.