Formation of p+-p−-n− junctions in InP by Cd diffusion

Abstract

A study was made of the diffusion of Cd into nominally undoped (4×10¹⁶ cm⁻³) n‐type InP using elemental sources consisting of (Cd and In) or (Cd and P). Two diffusion fronts whose depths are controlled by the amount of P or In in the diffusion source were delineated by etching. Electron beam induced current profiles and photoluminescence measurements revealed the formation of a p⁺‐ p⁻‐ n⁻ junction, with the p⁻ region bounded by the two diffusion fronts. Mesa p⁺‐ p⁻‐ n⁻ diodes, 150 μm in diameter, fabricated from a wafer with the p⁺‐ p⁻ and p⁻‐ n⁻ junctions at 3.1 and 20.0 μm, respectively, have reverse breakdown voltages between 90 and 220 V and reverse leakage currents from 5 to 10 pA at half breakdown. The I‐V characteristics of these p⁺‐p⁻‐n⁻ diodes exceed those of state of the art, abrupt p⁺‐n⁻ InP avalanche photodiodes because of the formation of the p⁻ region.