<i>p</i>-type conduction in Mg-doped GaN and Al0.08Ga0.92N grown by metalorganic vapor phase epitaxy

Tanaka, Toŝhiyuki; Watanabe, Atsushi; Amano, Hiroshi; Kobayashi, Yasufumi; Akasaki, Isamu; Yamazaki, Shunsuke; Koike, Masayoshi

doi:10.1063/1.112309

Cited by 263 publications

(144 citation statements)

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“…Several groups have reported successful MOCVD growth of uniform p-type AlGaN epitaxial layers using Mg as a dopant [8][9][10][11][12]. Most of the investigations focus on p-type AlGaN epilayers with an Al fraction that is less than 20%.…”

Section: Introductionmentioning

confidence: 99%

“…However, the achievement of high Al-content p-type AlGaN remains a significant challenge. Two main factors limit the p-type conductivity of AlGaN alloy: (i) the high activation energy for the substitutional Mg acceptor, the primary p-type dopant in GaN, is high (150-210 meV) [3][4][5], and becomes higher as the value of x in Al x Ga 1-x N increases [6]. (ii) When increasing the Al fraction, the AlGaN epi-layer usually exhibits higher defect densities [7], which can compensate for the dopants.…”

Section: Introductionmentioning

confidence: 99%

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MOCVD growth and electrical studies of p-type AlGaN with Al fraction 0.35

Yu¹,

Ulker²,

Özbay³

2006

Journal of Crystal Growth

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We present a study on the high performance p-type Al x Ga 1Àx N (x ¼ 0:35) layers grown by low-pressure metalorganic chemical vapor deposition on AlN template/sapphire substrate. The influence of growth conditions on the p-type conductivity of the Al x Ga 1Àx N (x ¼ 0:35) alloy is investigated. From the Hall effect and I-V transmission line model measurements, a p-type resistivity of 3.5 O cm for Al x Ga 1Àx N (x ¼ 0:35) epilayers are achieved. To the best of our knowledge, this is the lowest resistivity ever measured for the uniform p-type AlGaN with Al fraction higher than 0.3. The Mg and impurities (O, C and H) of the atom concentration in the epi-layers are analyzed by means of SIMS depth profiles, which reveal the dependence of impurities incorporation on the III elements and growth temperature. r

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

MOCVD growth and electrical studies of p-type AlGaN with Al fraction 0.35

Yu¹,

Ulker²,

Özbay³

2006

Journal of Crystal Growth

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“…A decrease of the hole mobility below 150 K has effectively been observed experimentally. [5][6][7][8][9] The exponent ␣ is considered as an additional parameter. In case of a temperature dependence imposed by impurity scattering, it is often given with a value of the order of 3/2.…”

Section: Microscopic Description Of the Junctionmentioning

confidence: 99%

“…The hole effective mass is fixed at m p ϭ0.8m 0 . 5 The parameters which remain to be determined are the Schottky barrier height q b at the two junctions, the position of the two levels E tA and E tB and their respective concentrations N tA and N tB , their thermal capture cross sections pA and pB and the factor R . The RT hole mobilty p has been fixed to 10 cm 2 /V s, with a (T/T 0 ) ␣ temperature dependence below T 0 ϭ150 K. We have not considered the mobility p as an independent parameter as the reduction factor R is already used.…”

Section: Admittance Curves Of the Back To Back Connected Schottky mentioning

confidence: 99%

“…The activation energy of the acceptor level related to the magnesium atoms has been measured by various experimental techniques leading to values between 70 and 250 meV, [2][3][4][5][6][7][8][9][10][11][12][13][14] which is much larger than for the impurities generally used as shallow dopants. As a consequence, Mg is not fully ionized at any temperature, and the resulting hole concentration is strongly temperature dependent.…”

Section: Introductionmentioning

confidence: 99%

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Thermal admittance spectroscopy of Mg-doped GaN Schottky diodes

Nguyen

Germain

Schmeits

et al. 2001

Journal of Applied Physics

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Thermal admittance spectroscopy measurements at temperatures ranging from room temperature to 90 K are performed on Schottky structures based on Mg-doped GaN layers grown by metalorganic vapor phase epitaxy on sapphire. The analysis of the experimental data is made by a detailed theoretical study of the steady-state and small-signal electrical characteristics of the structures. Numerical simulations are based on the solution of the basic semiconductor equations for the structure consisting of two Schottky diodes connected back to back by a conduction channel formed by the GaN layer. The description explicitly includes the Mg-related acceptor level, with its temperature-and position-dependent incomplete occupation state, leading to a dynamic exchange with the valence band. It fully reproduces the variations with temperature of the capacitancefrequency and conductance over frequency curves, allowing to give for all temperature ranges the origin of the various contributions to the junction capacitance and of the microscopic mechanisms responsible for the capacitance-frequency cutoff. Series resistance effects are shown to be dominant at temperatures above 230 K, whereas the Mg-related acceptor level governs the electrical behavior below 230 K. The existence of a second acceptor level with an activation energy of several tens of meV is revealed from the analysis of the characteristics at low temperature. An optimized fitting procedure based on the comparison of the electrical characteristics obtained from the numerical simulations to the experimental data allows one to determine the microscopic parameters describing the structure, among which the acceptor activation energies, thermal capture cross sections, concentrations, and the Schottky contact barrier heights are the most important ones. The obtained activation energy of the Mg-acceptor level of 210 meV is by a factor of 2 larger than that obtained from a classical Arrhenius plot, showing that a complete description of Mg-doped GaN junctions requires the correct treatment of the Mg level, acting as a dopant and as deep impurity, as well as the inclusion of series resistance effects.

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