Gain characteristics of InGaN quantum wells with AlGaInN barriers

Abstract

A reduction of the threshold current density of InGaN quantum well (QW) lasers is found from the usage of AlGaInN barriers. Large bandgap and strain-managing AlGaInN barriers surrounding the InGaN quantum wells’ (QWs) active regions are investigated via the 6-band self-consistent k·p formalism for their spontaneous emission, material gain, and threshold current density properties. In this study, quaternary AlGaInN alloys both lattice-matched and tensile-strained to GaN, with bandgaps ranging from 3.4 eV to 5.2 eV, are employed as thin barriers (∼1 nm) surrounding the InGaN active region. The AlGaInN barriers provide strong carrier confinement, which improves the electron and hole wavefunction overlap by ∼25%, while simultaneously reducing the strain relaxation in the active region. This study shows that InGaN QWs surrounded by AlGaInN barriers improve the material gain by ∼30%, reduce the threshold carrier density by ∼18%, and reduce the threshold current density by ∼40% over the conventional InGaN/GaN QW structure. Our results indicate that the AlGaInN barriers substantially enhance the radiative efficiency and reduce the power consumption for light emitting diodes (LEDs) and laser diodes (LDs), making them very attractive candidates for the design of low threshold optoelectronic devices.