Quantum-well width dependence of threshold current density in InGaN lasers

The quantum-confined Stark effect was found to result in a strong quantum-well width dependence of threshold current density in strained group-III nitride quantum well lasers. For an ${\mathrm{In}}_{\mathrm{0.2}}{\mathrm{Ga}}_{\mathrm{0.8}}\mathrm{N/GaN}$ structure with quantum-well width in the neighborhood of 3.5 nm, our analysis shows that the reduction in spontaneous emission loss by the electron–hole spatial separation outweighs the corresponding reduction in gain to produce a threshold current-density minimum.