Carrier localization and dynamics in In$_{0.10}$Ga$_{0.90}$N: the impact of alloying and Si doping

TL;DR

This study investigates how silicon doping affects carrier localization, optical properties, and defect structures in InGaN alloys, revealing that doping enhances luminescence and carrier confinement despite increasing disorder.

Contribution

It provides new insights into the effects of Si doping on disorder, localization, and optical performance in InGaN thin films, highlighting improved luminescence despite increased defect density.

Findings

Si doping increases edge dislocation density but not lattice parameters.

Doped samples show higher photoluminescence intensity and narrower linewidths.

Doping induces deeper localized states, enhancing carrier confinement.

Abstract

Alloying and doping are crucial for enhancing the electronic and optical properties of semiconductors while simultaneously introducing disorder. This report explores the effects of alloying and Si (0.5 at.\%) doping on In$_{0.10}$Ga$_{0.90}$N thin films that were grown by metal-organic vapor phase epitaxy. Post-growth X-ray diffraction measurements indicate that Si doping does not affect the lattice parameters and screw dislocations but significantly increases the edge dislocation density. Temperature-dependent time-resolved photoluminescence spectroscopy shows that Si-doped In$_{0.10}$Ga$_{0.90}$N exhibits higher photoluminescence intensity, blue-shifted peaks, narrower emission linewidths, and quenching of lower energy sidebands when compared to pristine In$_{0.10}$Ga$_{0.90}$N. The peak energies of the most dominant feature, the donor-bound exciton, for both samples show an $S$-shape behavior indicating the presence of disorder. Although doping improves luminescence, it also introduces deeper localized states. This suggests that impurity-induced disorder outweighs compositional fluctuations, as confirmed by higher disorder parameters and Stokes shifts. Thus, the Si doping leads to increased localization, reducing nonradiative recombination channels while enhancing radiative processes. The deeper states in the doped sample confirm improved carrier confinement, and their saturation leads to early thermalization, thereby lowering the red-blue shift transition from 165 K to about 50 K. Even though the high doping level makes Si-doped In$_{0.10}$Ga$_{0.90}$N a degenerate system, it exhibits enhanced luminescence properties. These findings shed light on the impact of silicon doping on charge transport in InGaN alloys for optoelectronic applications.