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

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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.