First laser diodes fabricated from III–V nitride based materials

InGaN multi-quantum well (MQW) structure laser diodes (LDs) were fabricated on A-face sapphire substrates. The stimulated emission of the LDs was not observed up to the threshold current of 160 mA, which corresponded to a threshold current densityof 5 kA cm−2. The operating voltage at the threshold current was around 20 V. Polarization measurements showed that the transverse electric-polarized light output intensity increased to a much larger value than the transverse magnetic-polarized light, above the threshold current. At injection currents below the threshold, spontaneous emission, which had a full width at half-maximum of 20 nm and a peak wavelength of 406.8 run, appeared. Above the threshold current, strong stimulated emissions were observed at a wavelength of 406.3 nm.