We have identified piezoelectric fields in strained GaInN/GaN quantum well p-in structures using the quantum-confined Stark effect. The photoluminescence peak of the quantum wells showed a blueshift with increasing applied reverse voltages. This blueshift is due to the cancellation of the piezoelectric field by the reverse bias field. We determined that the piezoelectric field points from the growth surface to the substrate and its magnitude is 1.2 MV/cm for Ga 0.84 In 0.16 N/GaN quantum wells on sapphire substrate. In addition, from the direction of the field, the growth orientation of our nitride epilayers can be determined to be ͑0001͒, corresponding to the Ga face.

The formation of pits in GaInN quantum wells (QWs) has been studied by atomic force microscopy and transmission electron microscopy. It is found that the pits have a hexahedron cone morphology with six sidewalls on 〈11̄01〉 planes and dislocations connected to their vertexes. The dislocations may induce the formation of pits during the growth of GaInN QWs.

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We have grown bulk GaAsN and InGaAsN quantum well laser structures using molecular beam epitaxy and an electron cyclotron resonance plasma source with N2 gas. X-ray diffraction measurements in GaAsN grown on GaAs were used to determine the concentration of N in the range of 0% to ∼2%. Room temperature photoluminescence (PL) measurements were done on quantum well test structures and half lasers. The PL intensity decreases and the PL full width at half maximum (FWHM) increases as the wavelength increases. Rapid thermal annealing (RTA) at 850 °C for 10 s improves the PL intensity by a factor of 8 and increases the PL peak emission energy by 80 meV. The longest wavelength measured to date in laser structures with single quantum wells of InGaAsN is 1480 nm with a FWHM of 60 meV. Samples with and without RTA were fabricated into broad-area lasers with dimensions of 50×500 μm2. Laser devices with RTA operated in the pulsed mode at 1.3 μm with a threshold current density of 9.5 kA/cm2.