Estimation of Shockley–Read–Hall Lifetime in Homoepitaxial n‐GaN on Low‐Dislocation‐Density GaN Substrates Prepared by Hydride Vapor Phase Epitaxy and Maskless 3D

Abstract

By eliminating the influence of surface recombination, the reported consideration that on‐resistance of GaN p+n diodes fabricated on free‐standing substrates should be limited by nonradiative recombination around dislocation lines is validated. The validation is based on analyses of 1) bulk nonradiative recombination current densities (Jnr), determined from the y intercept of forward‐current density/inverse of anode radius plots, of diodes fabricated on two kinds of vapor‐phase epitaxially grown freestanding substrates (i.e., maskless 3D [M‐3D, dislocation density Ndis ≤ 4 × 105 cm−2] and void‐assisted separation [VAS, Ndis = 1–4 × 106 cm−2]) and 2) distributions of two‐photon photoluminescence (2PPL) from an n‐GaN layer identifying dislocations as dark spots. Based on the extracted values of Jnr, the Shockley–Read–Hall lifetime of GaN p+n diodes on M‐3D and VAS substrates, and are, respectively, estimated to be 11 and 2 ns. Under the assumption of high excitation for the 2PPL measurement, the use of of 11 ns reproduces the 2PPL data with the effective dislocation radius ranging from 0.2 to 2 nm.

No significant contribution of hole-trap-enhanced conductivity modulation in GaN p+n diodes formed on low-dislocation-density GaN substrates

“…We used τ n of 5.3 ns and τ p of 23 ns that we derived from the Shockley-Read-Hall lifetime of 200−800 μm diameter GaN p + n diodes formed on M-3D substrates. 27) Note that τ p /τ n of 4.3 comes from σ p /σ n = 4.3 under the assumption σ n in n-GaN is the same as the reported σ n in p-GaN. 31,32) As for μ p , we used a fixed value of 29 cm 2 V −1 s −1 .…”

“…1(a)]. I F /V F characteristics were simulated at 300 K in reference to the cylindrical coordinate system 19,20,[27][28][29][30] by using the drift-diffusion model in a commercial device simulator, Silvaco ATLAS. We used τ n of 5.3 ns and τ p of 23 ns that we derived from the Shockley-Read-Hall lifetime of 200−800 μm diameter GaN p + n diodes formed on M-3D substrates.…”