Zn Diffusion in InxGa1-xAs with ZnAs2 Source

Abstract

By using ZnAs2 as a diffusion source, Zn has been diffused into InxGa1-xAs over the whole range of composition x at temperatures between 500°C and 600°C. The measured activation energy and crystal composition dependence of the diffusion coefficients and Zn surface concentration are compared with the two diffusion models so far proposed and are found to agree with the interstitial (Zni2+)-substitutional (Zns-) model. Empirical formulas describing the dependence of junction depth, hole concentration, hole mobility and diffused layer resistivity on crystal composition x, diffusion time t and temperature T are derived. Planar photodiodes, fabricated by preferential Zn diffusion in InxGa1-xAs VPE layers, exhibit microplasma-free uniform breakdown with higher breakdown voltage than 100 V, low junction capacitance of 0.24 pF for 100 µm diameter and low dark current density of 10-6 to 10-5 A/cm2.