Spatial distribution of free-carrier lifetime and deep-level luminescence across a semi-insulating GaAs wafer

Abstract

The free-carrier lifetime, the near band-edge luminescence (band-to-band and band-to-acceptor transitions), and the near-infrared deep-level luminescence (two bands at 0.7 and 0.8 eV) are mapped across an undoped semi-insulating GaAs wafer. The carrier lifetime follows on a large scale a W-shaped profile across the wafer with lifetimes varying between 200 and 500 ps at T=5 K. The band-to-band, band-to-acceptor, and the 0.7-eV luminescence are intense wherever the lifetime is long. However, the intensity of the 0.8-eV luminescence is high where the lifetime is short. The intensity variation of the 0.8-eV luminescence could quantitatively explain the lifetime distribution. Comparison with near-infrared absorption data show that EL20 as mapped by near-infrared absorption is not responsible for the short lifetime. Additionally, the lifetime shows a short-distance variation with a cell size of about 300 μm.