Current transport mechanisms in GaN-based metal–semiconductor–metal photodetectors

Carrano, John C.; Li, T.; Grudowski, P. A.; Eiting, C. J.; Dupuis, R. D.; Campbell, Joe C.

doi:10.1063/1.120752

Cited by 91 publications

(52 citation statements)

References 9 publications

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“…Surface states, which may be related to the polarization charge compensation, have a considerable effect on the failure mechanisms. The states may assist thermionic emission and/or thermionic field emission electron tunneling by acting as trapping centers 2,11 or pinning states that affect the Schottky barriers. 5,7 On the other hand, current collapse is ascribed to the formation of a virtual gate, which has been related to a change of the surface states.…”

Section: Introductionmentioning

confidence: 99%

Surface band bending and band alignment of plasma enhanced atomic layer deposited dielectrics on Ga- and N-face gallium nitride

Yang

Eller

Nemanich

2014

Journal of Applied Physics

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The effects of surface pretreatment, dielectric growth, and post deposition annealing on interface electronic structure and polarization charge compensation of Ga-and N-face bulk GaN were investigated. The cleaning process consisted of an ex-situ wet chemical NH 4 OH treatment and an in-situ elevated temperature NH 3 plasma process to remove carbon contamination, reduce oxygen coverage, and potentially passivate N-vacancy related defects. After the cleaning process, carbon contamination decreased below the x-ray photoemission spectroscopy detection limit, and the oxygen coverage stabilized at $1 monolayer on both Ga-and N-face GaN. In addition, Ga-and N-face GaN had an upward band bending of 0.8 6 0.1 eV and 0.6 6 0.1 eV, respectively, which suggested the net charge of the surface states and polarization bound charge was similar on Ga-and N-face GaN. Furthermore, three dielectrics (HfO 2 , Al 2 O 3 , and SiO 2 ) were prepared by plasma-enhanced atomic layer deposition on Ga-or N-face GaN and annealed in N 2 ambient to investigate the effect of the polarization charge on the interface electronic structure and band offsets. The respective valence band offsets of HfO 2 , Al 2 O 3 , and SiO 2 with respect to Ga-and N-face GaN were 1.4 6 0.1, 2.0 6 0.1, and 3.2 6 0.1 eV, regardless of dielectric thickness. The corresponding conduction band offsets were 1.0 6 0.1, 1.3 6 0.1, and 2.3 6 0.1 eV, respectively. Experimental band offset results were consistent with theoretical calculations based on the charge neutrality level model. The trend of band offsets for dielectric/GaN interfaces was related to the band gap and/or the electronic part of the dielectric constant. The effect of polarization charge on band offset was apparently screened by the dielectric-GaN interface states. V C 2014 AIP Publishing LLC.

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Section: Introductionmentioning

confidence: 99%

Surface band bending and band alignment of plasma enhanced atomic layer deposited dielectrics on Ga- and N-face gallium nitride

Yang

Eller

Nemanich

2014

Journal of Applied Physics

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“…In particular, leakage currents through Schottky contacts not only impede device reliability but also degrade power efficiency and noise performance in such devices. In spite of the fact that Schottky diodes formed on GaN and AlGaN are suffering from excess reverse leakage currents that are many orders of magnitude larger than the prediction of the thermionic emission ͑TE͒ model, [1][2][3][4][5][6] only a few studies have focused on the reverse-current characteristics quantitatively.…”

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confidence: 99%

“…Other groups also suggested the trap-assisted tunneling model to explain the leakage mechanism in the reverse bias region. 2,9 However, such model requires an unlikely multistep tunneling process or defect continuum with a wide energy band throughout a depletion region in semiconductor. Sawada et al 10 proposed a surface patch model to explain forward current characteristics.…”

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confidence: 99%

Leakage mechanism in GaN and AlGaN Schottky interfaces

Hashizume¹,

Kotani²,

Hasegawa³

2004

Applied Physics Letters

182

112

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Based on detailed temperature-dependent current-voltage (I -V -T) measurements the mechanism of leakage currents through GaN and AlGaN Schottky interfaces is discussed. The experiments were compared to calculations based on thin surface barrier model in which the effects of surface defects were taken into account. Our simulation method reproduced the experimental I -V -T characteristics of the GaN and AlGaN Schottky diodes, and gave excellent fitting results to the reported Schottky I -V curves in GaN for both forward and reverse biases at different temperatures. The present results indicate that the barrier thinning caused by unintentional surface-defect donors enhances the tunneling transport processes, leading to large leakage currents through GaN and AlGaN Schottky interfaces. © 2004 American Institute of Physics. ͓DOI: 10.1063/1.1762980͔ Although significant progress has been achieved in GaNbased high-power/high-frequency electronic devices and ultraviolet photodetectors, surface-related problems still need an immediate solution. In particular, leakage currents through Schottky contacts not only impede device reliability but also degrade power efficiency and noise performance in such devices. In spite of the fact that Schottky diodes formed on GaN and AlGaN are suffering from excess reverse leakage currents that are many orders of magnitude larger than the prediction of the thermionic emission ͑TE͒ model, 1-6 only a few studies have focused on the reverse-current characteristics quantitatively.Yu et al. 7 and Miller et al. 8 discussed the leakage mechanism in GaN and AlGaN Schottky interfaces on the basis of the field-emission ͑FE͒ tunneling transport assuming a triangular Schottky potential. However, unreasonably higher donor densities than the actual doping concentration were required in their calculation for reproduction of the experimental data. Thus, they expected some other processes such as defect-assisted tunneling to enhance leakage currents. Other groups also suggested the trap-assisted tunneling model to explain the leakage mechanism in the reverse bias region. 2,9 However, such model requires an unlikely multistep tunneling process or defect continuum with a wide energy band throughout a depletion region in semiconductor. Sawada et al. 10 proposed a surface patch model to explain forward current characteristics. Miller et al. 11 have recently suggested a leakage mechanism associated with a variablerange-hopping conduction through threading dislocations. However, little is known for the physical mechanism of excess leakage currents in GaN and AlGaN Schottky diodes.This letter discusses the mechanism of leakage currents through GaN Schottky interfaces, investigating transport properties of Schottky diodes using temperature-dependent current-voltage (I -V -T) measurements for both forward and reverse biases. A simulation method for the calculation of currents based on the thin surface barrier ͑TSB͒ model 5 is discussed. The measured currents were compared to the calculated ones for different tempe...

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“…The defect related tunneling is attributed to a combination of interface states and deep level traps that are within a tunneling distance of the interface [31]. The deep level traps are attributed to the contamination layer on clean GaN and threading dislocations that reach the surface.…”

Section: B Forward Conductionmentioning

confidence: 99%