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.

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A concept for a short-wavelength compact laser is proposed, in which second-harmonic coherent light is produced by converting fundamental light lased in a vertical-cavity surface-emitting laser. A layer is incorporated inside the laser cavity particularly for efficient second-harmonic generation. This layer consists of second-order optical nonlinear crystals which are preferably III–V- or II–VI-system compound semiconductors epitaxially grown with crystal orientation tilted from <100>. Simulation indicates that the device will produce several hundred µ W with AlAs/GaAs alternating layers for second-harmonic generation and an InGaAs active layer for lasing.