Growth conditions have a tremendous impact on the unintentional background impurity concentration in gallium nitride (GaN) synthesized by molecular beam epitaxy and its resulting chemical and physical properties. In particular for oxygen identified as the dominant background impurity we demonstrate that under optimized growth stoichiometry the growth temperature is the key parameter to control its incorporation and that an increase by 55 °C leads to an oxygen reduction by one order of magnitude. Quantitatively this reduction and the resulting optical and electrical properties are analyzed by secondary ion mass spectroscopy, photoluminescence, capacitance versus voltage measurements, low temperature magneto-transport and parasitic current paths in lateral transistor test structures based on two-dimensional electron gases. At a growth temperature of 665 °C the residual charge carrier concentration is decreased to below 1015 cm-3, resulting in insulating behavior and thus making the material suitable for beyond state-of-the-art device applications.
Keywords: 100 Materials; 103 Composites; 105 Low-Dimension (1D/2D) materials; 200 Applications; 201 Electronics / Semiconductor / TCOs; 300 Processing / Synthesis and Recycling; 302 Crystallization / Heat treatment / Crystal growth; 40 Optical, magnetic and electronic device materials; 500 Characterization; 501 Chemical analyses; 505 Optical / Molecular spectroscopy; GaN; MBE; oxygen incorporation.