Indium-surfactant-assisted growth of high-mobility AlN/GaN multilayer structures by metalorganic chemical vapor deposition

Abstract

AlN/GaN single and multilayer structures with various AlN and GaN layer thicknesses were grown by metalorganic chemical vapor deposition. Step flow growth of AlN was achieved using trimethylindium as a surfactant. Defect formation in the AlN layer could be largely prevented for AlN layers thinner than 2.9 nm. In the multiquantum-well samples, which consisted of five (AlN/GaN) periods, a two-dimensional electron gas (2DEG) was formed at the interface between the GaN base layer and the first AlN barrier layer. When the thickness of the AlN barrier layer in the multiquantum well was increased from 0.9 to 2.6 nm at a constant GaN well thickness of 5 nm, the sheet carrier density of the 2 DEG increased from 5×1012 to 2.1×1013 cm−2 and the electron mobility measured at 77 K decreased from 11780 to 3140 cm2/V s. The effect of the GaN well thickness was also investigated.

Aluminum incorporation in -layers and implications for growth optimization

“…Some undoped layers were grown for comparison. In some cases Al x Ga 1Àx N layers were grown with trimethylindium (TMIn) in the background to enhance the lateral to vertical growth rates (may act as surfactant as well [10]). As nucleation layers AlN and InGaN were used.…”

Growth of AlxGa1−xN-layers on planar and patterned substrates

“…Diluted SiH 4 is used for n-type doping. In some cases, Al x Ga 1Àx N layers were grown with trimethylindium (TMIn) in the background to enhance the lateral to vertical growth rates (may act as surfactant as well [6]). SiC: growth started with a thin (10-50 nm thick) Al x Ga 1Àx N nucleation layer grown at 1190 1C with x $ 0:3 ramped down to x $ 0:2 or an AlN buffer layer of thickness 100 nm.…”

Intrinsic degradation mechanism of nearly lattice-matched InAlN layers grown on GaN substrates

“…42 Particularly, In was proposed to improve the Al surface mobility through this effect. 43 Thus increasingthe In/Al flux ratio has the same rolethan increasing the temperature: it decreasesthe kinetic roughening, 41 and it delays the appearance of V-defects.Before going further in the discussion concerning the formation mechanism of V-defects, let us analyze their structure and the degradation mechanism of the layers with increasing thickness as deduced from TEM observations.…”