Forming Low-Resistance p-Type Layers in Ga1 – xAlxN/GaN Heterostructures

A technique for fabricating a GaN-based functional heterostructure is proposed, which allows the growth of n -type GaN and In x Ga 1 – x N layers and р -type GaN and Al x Ga 1 – x N layers. At present, the fabrication of n -type layers does not poseany serious technological difficulties, while the fabrication of p -GaN layers is a great challenge. It is shown that, thermodynamically, when forming acceptor-doped GaN (with a high NH 3 excess) using metalorganic compounds, ( А -Н) 0 neutral complexes in high concentrations can be formed. It is found that a decrease in the concentration of an acceptor and, consequently, hydrogen, in the layers leads to a decrease in the concentration of neutral complexes and simplifies the technological task of obtaining low-resistance р -type layers even at low acceptor concentrations. However, this requires new technological approaches to reducing the content of hydrogen and impurities, e.g., Si, O 2 , and С, during GaN epitaxy. The optimal consumption of Cp 2 Mg corresponding to the maximum attainable magnesium concetration ((6–8) × 10 20 cm –3 ) in the epitaxial layer is about 20–30 L/min. To obtain the maximum quantum yield, the heterostructures should be annealed in a narrow temperature range (1063–1073 K).