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

TL;DR

This work investigates how alloying and Si doping influence carrier localization and dynamics in In$_{0.10}$Ga$_{0.90}$N. By combining high-resolution XRD and temperature-dependent TD-TRPL, the authors disentangle alloy- and impurity-induced disorder using the LSE model and Varshni fits. They find that In-induced alloy disorder creates shallow localized states, while Si doping introduces deeper impurity traps that sharpen localization, blueshift donor-bound exciton emission, and increase radiative efficiency, albeit with a degenerate carrier system evidenced by Burstein–Moss effects. These results highlight how controlled Si doping can optimize radiative processes in InGaN for UV/blue optoelectronic devices, while maintaining useful localization physics for carrier transport applications.

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.

Figures (5)

• Figure 1: HR-XRD: (a) 2$\theta-\omega$ scan and (b) reciprocal space maps of In$_{0.10}$Ga$_{0.90}$N (top) and In$_{0.10}$Ga$_{0.90}$N:Si (bottom).
• Figure 2: The PL spectra of In$_{0.10}$Ga$_{0.90}$N and In$_{0.10}$Ga$_{0.90}$N:Si measured 10 K.
• Figure 3: The PL spectra showing in (a$_1$) and (a$_2$) the full temperature range for In$_{0.10}$Ga$_{0.90}$N and In$_{0.10}$Ga$_{0.90}$N:Si, respectively. (b) and (c) illustrate the representative Gaussian fitted spectra at selected temperatures for each sample, in that order.
• Figure 4: Extracted peak energy positions against temperature fitted with the LSE model and Varshni's equation for (a) In$_{0.10}$Ga$_{0.90}$N and (b) In$_{0.10}$Ga$_{0.90}$N:Si
• Figure 5: The temporal evolution of the transient spectra and intensity of In$_{0.10}$Ga$_{0.90}$N (top) and In$_{0.10}$Ga$_{0.90}$N:Si (bottom). Shown in (a$_1$) and (a$_2$) are the spectra obtained from TD-TRPL measurements, (b$_1$) and (b$_2$) depict the extracted $\tau_1$ and $\tau_2$ parameters for the samples, including their respective intensity curves. Lastly, the fitted thermal quenching of the PL intensity in (c$_1$) and (c$_2$).