Free-carrier screening of polarization fields in wurtzite GaN/InGaN laser structures

TL;DR

This paper investigates how free carriers in wurtzite GaN/InGaN laser structures screen polarization fields, revealing a field-free band profile that explains high thresholds and blue-shifts in emission.

Contribution

It demonstrates through a self-consistent tight-binding model that high carrier concentrations effectively screen polarization fields in nitride laser structures.

Findings

Screening of polarization fields leads to a field-free band profile.

High carrier concentrations explain high lasing thresholds.

Emission blue-shifts with increased excitation are accounted for.

Abstract

The free-carrier screening of macroscopic polarization fields in wurtzite GaN/InGaN quantum wells lasers is investigated via a self-consistent tight-binding approach. We show that the high carrier concentrations found experimentally in nitride laser structures effectively screen the built-in spontaneous and piezoelectric polarization fields, thus inducing a ``field-free'' band profile. Our results explain some heretofore puzzling experimental data on nitride lasers, such as the unusually high lasing excitation thresholds and emission blue-shifts for increasing excitation levels.