Measuring the Minority-Carrier Diffusion Length of n-Type In0.53Ga0.47As Epilayers Using Surface Photovoltage

Abstract

We report measurements of the minority-carrier diffusion length of n-type In0.53Ga0.47As epilayer samples using the surface photovoltage (SPV) method, and the minority-carrier lifetime of the same samples obtained by the microwave photoconductivity decay (μ-PCD) method. The minority-carrier diffusion length was determined from the surface photovoltage and the optical absorption coefficient of the material. By scanning the SPV probe over the sample, the difference in surface photovoltage could be measured, as well as enabling surface photovoltage mapping. Samples having two different doping concentrations were used: sample A with 3 × 1016 cm−3 and sample B with 1 × 1016 cm−3, having minority-carrier diffusion length at room temperature of 5.59 μm and 6.3 μm, respectively. Meanwhile, sample uniformity was investigated using SPV for the first time. Lifetime measurements were performed on the n-type In0.53Ga0.47As epilayer samples using the μ-PCD technique, obtaining the minority-carrier diffusion length indirectly. Comparison of the minority-carrier diffusion length values obtained from SPV versus μ-PCD showed good consistency. Therefore, the presented method could be useful for characterization of the minority-carrier diffusion length of wafers.