Publication Date:
2016-09-09
Description:
In the low doping range below 1 × 10 17 cm −3 , carbon was identified as the main defect attributing to the sudden reduction of the electron mobility, the electron mobility collapse, in n-type GaN grown by low pressure metalorganic chemical vapor deposition. Secondary ion mass spectroscopy has been performed in conjunction with C concentration and the thermodynamic Ga supersaturation model. By controlling the ammonia flow rate, the input partial pressure of Ga precursor, and the diluent gas within the Ga supersaturation model, the C concentration in Si-doped GaN was controllable from 6 × 10 19 cm −3 to values as low as 2 × 10 15 cm −3 . It was found that the electron mobility collapsed as a function of free carrier concentration, once the Si concentration closely approached the C concentration. Lowering the C concentration to the order of 10 15 cm −3 by optimizing Ga supersaturation achieved controllable free carrier concentrations down to 5 × 10 15 cm −3 with a peak electron mobility of 820 cm 2 /V s without observing the mobility collapse. The highest electron mobility of 1170 cm 2 /V s was obtained even in metalorganic vapor deposition-grown GaN on sapphire substrates by optimizing growth parameters in terms of Ga supersaturation to reduce the C concentration.
Print ISSN:
0021-8979
Electronic ISSN:
1089-7550
Topics:
Physics
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