InGaN/GaN/AlGaN-Based Laser Diodes Grown on GaN Substrates with a Fundamental Transverse Mode

An InGaN multiquantum-well (MQW)-structure laser diode (LD) was grown on an epitaxially laterally overgrown GaN on sapphire. The lowest threshold current densities between 1.2 and 2.8 kA/cm2 were obtained when the number of InGaN well layers was two. The InGaN MQW LD was grown on a free-standing GaN substrate that was obtained by removing the sapphire substrate. The LDs with cleaved mirror facets showed an output power as high as 30 mW under room-temperature continuous-wave (CW) operation. The stable fundamental transverse mode was observed by reducing the ridge width to a value as small as 2 µm. The lifetime of the LDs at a constant output power of 5 mW was about 160 h under CW operation at an ambient temperature of 50°C, due to a high threshold current density of 6 kA/cm2.