Characterization of AlGaN-Schottky Diodes Grown by Plasma Induced Molecular Beam Epitaxy

Karrer, U.; Dobner, A.; Ambacher, O.; Stutzmann, M.

doi:10.1002/(sici)1521-396x(199911)176:1<163::aid-pssa163>3.0.co;2-u

Cited by 5 publications

(2 citation statements)

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“…High-quality Schottky barriers to n-type AlGaN are important for the efficient operation of ultraviolet photodetectors or heterostructure field-effect transistors (HFETs). [1][2][3][4] Several publications report the barrier height for Schottky contacts to n-AlGaN, [5][6][7][8][9][10][11][12][13] including three studies of the influence of the Al mole fraction on the barrier height, 8,11,12 where the increase in Al mole fraction (x Ͻ 0.35) provides higher Schottky barriers over those of pure n-GaN. Other more recent publications report on the thermal stability of Schottky barriers for gate metallizations on HFETs.…”

Section: Introductionmentioning

confidence: 99%

Environmental sensitivity of Au diodes on n-AlGaN

Readinger

Mohney

2005

Journal of Elec Materi

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With growing interest in AlGaN for ultraviolet detectors and high-power/hightemperature electronic devices, the problem of forming high-quality Schottky contacts to this semiconductor has become increasingly important. It was shown that wet-chemical surface pretreatments affect the as-deposited diode characteristics for Au/n-AlGaN Schottky diodes. However, these diodes improve over the course of days when exposed to air at room temperature, exhibiting reduced leakage currents, enhanced barrier heights, and reduced ideality factors. Exposure to oxygen, with an enhanced effect in the presence of water vapor, is responsible for the environmental aging. The environmental aging was found to occur regardless of the source of AlGaN, surface preparation, and metal deposition technique. It was determined that high asdeposited reverse currents were due to current transport beneath the contact area, rather than across the semiconductor surface. Two findings further suggested that the change in electrical characteristics was due to a phenomenon occurring at the metal/semiconductor interface. First, metal thickness played a key role in the rate of change of the electrical characteristics, with thicker contacts being more impervious to surrounding gas species at room temperature. Second, a metal that readily forms an oxide, Ni, exhibited little environmental aging, while noble metals, such as Au and Pt, showed dramatic effects. Mild anneals revealed that the environmental change was partially reversible, which suggests the passivation of electrically active defects at the metal/semiconductor interface as the cause of the altered diode behavior. Taken together, the data indicate that oxidizing species diffuse through noble metal contacts to the metal/semiconductor interface and passivate electrically active defects, which may be reactivated upon mild anneals in N 2 .

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Section: Introductionmentioning

confidence: 99%

Environmental sensitivity of Au diodes on n-AlGaN

Readinger

Mohney

2005

Journal of Elec Materi

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“…Studies on contacts to AlGaN or AlGaN/GaN HFETs have been based on the Ti/Al, [7][8][9][10][11][12][13][14][15][16][17][18][19][20] NiAl, 21 and Pd/Al 7 metallization schemes with different overlayers for the ohmic contacts and on Ti, 22 Ni, [22][23][24] Pd, 25 Re, 26 Ir, 14,17,19 Pt, 16,25 Pt/Ti, 14 Au, [27][28][29] and WSiN 14 for the Schottky contacts. The choice of systems has been highly motivated by successful contact formation to GaN by these metallization schemes, and the studies have mainly been concerned with optimizing the electrical properties, i.e., low contact resistivity or high barrier heights, and thermal stability on nAl x Ga 1-x N with x ≤ 35%.…”

Section: Introductionmentioning

confidence: 99%

Phase equilibria in transition metal Al-Ga-N systems and thermal stability of contacts to AlGaN

Schweitz

Mohney

2001

Journal of Elec Materi

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As a first step in predicting the phase equilibria in TM-Al-Ga-N systems, where TM denotes a transition metal from the first three transition series, phase equilibria are calculated in the TM-Al-N systems, and the condensed phases in equilibrium with both AlN and N 2 gas are discussed with respect to the position of the transition metal in the periodic table, temperature, and nitrogen pressure. Possible phases for use as stable electrical contacts to AlGaN are identified using these predictions, similar previous predictions for the TM-Ga-N systems and experimental findings. fraction increases, the electronic properties of the existing contacts change due to an increasing band gap and decreasing electron affinity of AlGaN, and new metallization schemes may have to be developed to accomplish good contact formation to Al x Ga 1-x N with x > 35%. New metallization schemes may also turn out to yield contacts to Al x Ga 1-x N with x ≤ 35% with superior properties to the existing contacts.The phase equilibria in the TM-Ga-N systems, where TM denotes a transition metal from the first three transition series, have previously been estimated. 30 As a first step in understanding the TM-AlGa-N systems, this article discusses the phase equilibria in the TM-Al-N systems. There are fortunately more experimentally available phase diagrams for these systems 31-42 than for the TM-Ga-N system; 30,43-47 however, many of the diagrams are not available for the conditions of most interest for processing contacts and devices. Thus, calculated ternary phase diagrams have to be used in many cases. Such an approach has been taken for systems composed of transition metals and Al-As, 48,50 In-P, 51,52 and In-As; 48,49 however, the same simple approach that has been used to calculate the ternary phase diagrams is not possible for the TM-Al-Ga-N systems due to lack of information about quarternary phases and the predominance of solution phases in the TM-Al-Ga and AlGa-N systems.This paper presents simple ternary phase diagram calculations of the TM-Al-N systems. These calcula-

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