Correlation between mobility collapse and carbon impurities in Si-doped GaN grown by low pressure metalorganic chemical vapor deposition

Abstract

In the low doping range below 1 × 1017 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 × 1019 cm−3 to values as low as 2 × 1015 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 1015 cm−3 by optimizing Ga supersaturation achieved controllable free carrier concentrations down to 5 × 1015 cm−3 with a peak electron mobility of 820 cm2/V s without observing the mobility collapse. The highest electron mobility of 1170 cm2/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.

Ultrawide‐Bandgap Semiconductors: Research Opportunities and Challenges

“…The AlGaN alloys have exceptionally good fundamental physical properties. From an electronics perspective, they have (1) direct bandgaps spanning a wide range (3.4 to ≈6.0 eV), (2) high breakdown fields (>10 MV cm −1 for AlN), (3) high electron mobility (bulk mobilities up to 1000 cm 2 V −1 s −1 ), (4) high saturation velocities (>10 7 cm s −1 ), and (5) relative ease at being doped n‐type with Si, which has a relatively small donor ionization energy up to ≈80–85% Al content . From an optoelectronics perspective, these alloys offer direct access to emission wavelengths shorter than about 365 nm, that is, into the UV‐A, ‐B, and ‐C bands.…”

“…From an electronics perspective, they have (1) direct bandgaps spanning a wide range (3.4 to ≈6.0 eV), (2) high breakdown fields (>10 MV cm −1 for AlN), (3) high electron mobility (bulk mobilities up to 1000 cm 2 V −1 s −1 ), (4) high saturation velocities (>10 7 cm s −1 ), and (5) relative ease at being doped n-type with Si, which has a relatively small donor ionization energy up to ≈80-85% Al content. [24][25][26][27][28][29][30][31][32] From an optoelectronics perspective, these alloys offer direct access to emission Table 1. Selected materials properties of WBG and UWBG semiconductors, including present-day states-of-the-art in key metrics of material quality and manipulability: substrate dislocation density, substrate diameter, and bulk p-and n-type doping levels.…”

Growth and Properties of Intentionally Carbon‐Doped GaN Layers

“…[2] Its control is crucial for layers with low doping levels and nonuniform incorporation of carbon can reduce the breakdown voltage of electronic devices dramatically. [3][4][5][6] Carbon is suspicious to be related to current collapse and dispersion in transistors when used intentionally in highly resistive buffer layers. [7,8] Thus, the electronic properties of carbon in GaN remain of high interest.…”

Bulk and Surface Electronic Properties of Inorganic Materials: Tools to Guide Cellular Behavior

“…Furthermore, it has to be noted that DX‐type states producing PPC in AlGaAs are not observed in GaN and Ga‐rich AlGaN. Yellow luminescence originally attributed to PPC has been demonstrated to be due to C N, V Ga or their complexes, and not due to DX, nitrogen antisites, or structural defects …”