Generation of hole gas in non-inverted InAl(Ga)N/GaN heterostructures

InAlN/GaN structures are grown using organometallic chemical vapor deposition at 730 °C. The sample for which the chamber cleaning step was applied after GaN growth shows a sharp In0.3Al0.7N/GaN transition, free electron density of ~2 × 1011 cm−2 and mobility of 44 cm2 V−1 s−1. On the other hand, the sample prepared without growth interruption demonstrated In0.4Al0.15Ga0.45N at the interface and compositional grading towards the In0.4Al0.6N surface. In this case a two-dimensional hole gas (2DHG) is created with a density of ~2 × 1012 cm−2 and mobility of ~0.6 cm2 V−1 s−1. Ga incorporation in the InAlN barrier is crucial for designing non-inverted 2DHG transistors.