Optical microprobe response of GaAs diodes

GaAs p-n junction photocurrent response is obtained from an optical microprobe with a dynamic range of at least three decades and a light-spot diameter of about 1.3 µm. The results are found to correlate well with the appropriate theoretical response which includes surface recombination and assumed infinite absorption coefficient. Minority-carrier diffusion lengths computed from the data are typically 3.5 and 0.7 µm for holes in n-type material doped 10¹⁷and 1.4×10¹⁸cm^-3and 1 µm for electrons in >10¹⁸cm^-3doped p-type material. Estimates of carrier lifetimes are made and the deviation of surface recombination velocity between devices is demonstrated.