Band Gap States in AlGaN/GaN Hetero-Interface Studied by Deep-Level Optical Spectroscopy

2009 ◽  
Vol 1202 ◽  
Author(s):  
Yoshitaka Nakano ◽  
Keiji Nakamura ◽  
Yoshihiro Irokawa ◽  
Masaki Takeguchi
Keyword(s):  
Steady State ◽  
Optical Spectroscopy ◽  
Deep Level ◽  
Electron Gas ◽  
Two Dimensional ◽  
Dimensional Electron ◽  
Two Dimensional Electron Gas ◽  
Capacitance Voltage ◽  
Dimensional Electron Gas ◽  
Gap States

AbstractPlanar Pt/AlGaN/GaN Schottky barrier diodes (SBDs) have been characterized by capacitance-voltage and capacitance deep-level optical spectroscopy measurements, compared to reference Pt/GaN:Si SBDs. Two specific deep levels are found to be located at ∼1.70 and ∼2.08 eV below the conduction band, which are clearly different from deep-level defects (Ec - 1.40, Ec - 2.64, and Ec - 2.90 eV) observed in the Pt/GaN:Si SBDs. From the diode bias dependence of the steady-state photocapacitance, these levels are believed to stem from a two-dimensional electron gas (2DEG) region at the AlGaN/GaN hetero-interface. In particular, the 1.70 eV level is likely to act as an efficient generation-recombination center of 2DEG carriers.

Carbon-Related Deep-Level Defects and Turn-On Recovery Characteristics in AlGaN/GaN Hetero-Structures

2014 ◽  
Vol 1635 ◽  
pp. 109-114
Author(s):  
Yoshitaka Nakano ◽  
Yoshihiro Irokawa ◽  
Masatomo Sumiya ◽  
Yasunobu Sumida ◽  
Shuichi Yagi ◽  
...  
Keyword(s):  
Buffer Layer ◽  
Deep Level ◽  
Electron Gas ◽  
Two Dimensional ◽  
Dimensional Electron ◽  
Impurity Incorporation ◽  
Two Dimensional Electron Gas ◽  
Turn On ◽  
Dimensional Electron Gas ◽  
Gan Buffer Layer

ABSTRACTWe have investigated on a relation between C-related deep-level defects and turn-on recovery characteristics in bulk regions of AlGaN/GaN hetero-structures containing various C concentrations, employing their Schottky barrier diodes. With decreasing the growth temperature of the GaN buffer layer, three specific deep-level defects located at ∼2.07, ∼2.75, and ∼3.23 eV below the conduction band were significantly enhanced probably due to the C impurity incorporation into the GaN buffer layer. Among them, the ∼2.75 and ∼3.23 eV levels are considered to be strongly responsible for the two-dimensional electron gas (2DEG) carrier trapping in the bulk regions of the hetero-structures, from their turn-on current recovery characteristics under various optical illuminations.

Perturbation of charges in AlGaN/GaN heterostructures studied by nanoscale capacitance-voltage technique

2005 ◽  
Vol 892 ◽  
Author(s):  
Goutam Koley ◽  
Lakshminarayanan Lakshmanan
Keyword(s):  
Electron Gas ◽  
Two Dimensional ◽  
Dimensional Electron ◽  
Two Dimensional Electron Gas ◽  
Dc Voltage ◽  
Surface And Interface ◽  
Voltage Sweep ◽  
Uv Illumination ◽  
Capacitance Voltage ◽  
Dimensional Electron Gas

AbstractPerturbation of charges at the surface and interface of AlGaN/GaN heterostructures has been studied by quantitative nanoscale capacitance-voltage (C-V) measurements. The nanoscale C-V curves were found to have different slopes in the forward and reverse directions. These measurements indicate a change in confinement of the two-dimensional electron gas (2DEG) at the AlGaN/GaN interface depending on the direction of the dc voltage sweep during C-V measurements, which can be explained by surface state charging and discharging during the bias sweep. Under UV illumination, the density of the 2DEG increased significantly as inferred from the increase in threshold voltage of the nanoscale C-V scans, and no change in 2DEG confinement, depending on the direction of the bias sweep, was observed.

Nanoscale Capacitance-Voltage Characterization of Two-Dimensional Electron Gas in AlGaN/GaN Heterostructures

2005 ◽  
Vol 44 (No. 44) ◽  
pp. L1348-L1351 ◽  
Author(s):  
G. Koley ◽  
L. Lakshmanan ◽  
N. Tipirneni ◽  
M. Gaevski ◽  
A. Koudymov ◽  
...  
Keyword(s):  
Electron Gas ◽  
Two Dimensional ◽  
Dimensional Electron ◽  
Two Dimensional Electron Gas ◽  
Capacitance Voltage ◽  
Dimensional Electron Gas

Hydrostatic and uniaxial stress dependence and photo induced effects on the channel conductance of n-A1GaN/GaN heterostructures grown on sapphire substrates

1999 ◽  
Vol 572 ◽  
Author(s):  
A. K. Fung ◽  
C. Cai ◽  
P. P. Ruden ◽  
M. I. Nathan ◽  
M. Y. Chen ◽  
...  
Keyword(s):  
Deep Level ◽  
Hydrostatic Stress ◽  
Electron Gas ◽  
Uniaxial Stress ◽  
Organic Chemical ◽  
Two Dimensional ◽  
Dimensional Electron ◽  
Channel Conductance ◽  
Two Dimensional Electron Gas ◽  
Dimensional Electron Gas

ABSTRACTWe measure the hydrostatic stress, uniaxial stress, and photo induced dependence of the channel conductance of two-dimensional electron gas AlGaN/GaN heterostructures grown on c-axis sapphire. The structures examined are grown by nitrogen-plasma molecular beam epitaxy and metal organic chemical vapor deposition. Electrical conductance measurements are made with four point probes on Hall bar samples. Both, hydrostatic stress and uniaxial stress result in changes in the conductance. Moreover, these changes in conductance have long settling times after the stress is applied and may be due to deep level defects, the energy levels of which change with stress. Stress coefficients extracted from the samples are partially attributed to deep level defects and to the piezoelectric effect resulting from different piezoelectric coefficients of GaN and AlN. Photo induced changes of the two-dimensional electron gas are also observed. We find that pulsed illumination produces long transient times in the conductance. These transients are reduced by thermal heating in some samples. However, they can still be present at 153°C.

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