Shallow and Deep Level Defects in GaN

1995 ◽  
Vol 395 ◽  
Author(s):  
W. Götz ◽  
N.M. Johnson ◽  
D.P. Bour ◽  
C. Chen ◽  
H. Liu ◽  
...  
Keyword(s):  
Deep Level ◽  
Variable Temperature ◽  
Shallow Donor ◽  
Deep Levels ◽  
Electron Photoemission ◽  
Hall Effect Measurements ◽  
Transient Spectroscopy ◽  
P Type ◽  
Capacitance Transient ◽  
Threshold Energies

ABSTRACTShallow and deep electronic defects in MOCVD-grown GaN were characterized by variable temperature Hall effect measurements, deep level transient spectroscopy (DLTS) and photoemission capacitance transient spectroscopy (O-DLTS). Unintentionally and Si-doped, n-type and Mg-doped, p-type GaN films were studied. Si introduces a shallow donor level into the band gap of GaN at ∼Ec - 0.02 eV and was found to be the dominant donor impurity in our unintentionally doped material. Mg is the shallowest acceptor in GaN identified to date with an electronic level at ∼Ev + 0.2 eV. With DLTS deep levels were detected in n-type and p-type GaN and with O-DLTS we demonstrate several deep levels with optical threshold energies for electron photoemission in the range between 0.87 and 1.59 eV in n-type GaN.

Deep Level Defects in GaN Characterized by Capacitance Transient Spectroscopies

1995 ◽  
Vol 378 ◽  
Author(s):  
W. Gütz ◽  
N. M. Johnson ◽  
R. A. Street ◽  
H. Amano ◽  
I. Akasaki
Keyword(s):  
Thermal Activation ◽  
Deep Level ◽  
Schottky Diodes ◽  
Deep Levels ◽  
Electron Photoemission ◽  
Transient Spectroscopy ◽  
Capacitance Transient ◽  
Electronic Defects ◽  
Threshold Energies

AbstractElectronic defects in MOCVD-grown n-type GaN were characterized by conventional deep level transient spectroscopy (DLTS) and by photoemission capacitance transient spectroscopy (O-DLTS) performed on Schottky diodes. With DLTS two deep levels were detected with thermal activation energies for electron emission to the conduction band of 0.16 eV and 0.44 eV. With O-DLTS we demonstrate four new deep levels with optical threshold energies for electron photoemission of ∼ 0.87 eV, 0.97 eV, 1.25 eV and 1.45 eV. The O-DLTS apparatus and the measurement are discussed in detail. We also report characterization of the Au-GaN barrier height of the Schottky diode by internal photoemission.

Deep Levels Observed in High-Purity Semi-Insulating 4H-SiC

2010 ◽  
Vol 645-648 ◽  
pp. 455-458 ◽  
Author(s):  
Giovanni Alfieri ◽  
Tsunenobu Kimoto ◽  
Gerhard Pensl
Keyword(s):  
High Purity ◽  
Deep Level ◽  
Electrical Characterization ◽  
Current Mode ◽  
Deep Levels ◽  
Light Illumination ◽  
Hall Effect Measurements ◽  
Transient Spectroscopy ◽  
P Type

We report on the electrical characterization of high-purity semi-insulating 4H-SiC after annealing at temperatures between room temperature and 1700 oC by current-mode deep level transient spectroscopy (I-DLTS). I-V and Hall-effect measurements revealed that the investigated substrates possess p-type conductivity. Four deep levels were detected by I-DLTS with activation energies in the 0.15-1.29 eV range. We studied their thermal stability as well as their stability with respect to light illumination.

Reactive-Ion-Etching Induced Deep Levels Observed in n-Type and p-Type 4H-SiC

2010 ◽  
Vol 645-648 ◽  
pp. 759-762
Author(s):  
Koutarou Kawahara ◽  
Giovanni Alfieri ◽  
Michael Krieger ◽  
Tsunenobu Kimoto
Keyword(s):  
Deep Level Transient Spectroscopy ◽  
Deep Level ◽  
Reactive Ion Etching ◽  
Deep Levels ◽  
Total Density ◽  
Ion Etching ◽  
Initial Concentration ◽  
Grown Sample ◽  
Transient Spectroscopy ◽  
P Type

In this study, deep levels are investigated, which are introduced by reactive ion etching (RIE) of n-type/p-type 4H-SiC. The capacitance of as-etched p-type SiC is remarkably small due to compensation or deactivation of acceptors. These acceptors can be recovered to the initial concentration of the as-grown sample after annealing at 1000oC. However, various kinds of defects remain at a total density of ~5× 1014 cm-3 in a surface-near region from 0.3 μm to 1.0 μm even after annealing at 1000oC. The following defects are detected by Deep Level Transient Spectroscopy (DLTS): IN2 (EC – 0.35 eV), EN (EC – 1.6 eV), IP1 (EV + 0.35 eV), IP2 (HS1: EV + 0.39 eV), IP4 (HK0: EV + 0.72 eV), IP5 (EV + 0.75 eV), IP7 (EV + 1.3 eV), and EP (EV + 1.4 eV). These defects generated by RIE can be significantly reduced by thermal oxidation and subsequent annealing at 1400oC.

Deep Levels in P-Type 4H-SiC Induced by Low-Energy Electron Irradiation

2013 ◽  
Vol 740-742 ◽  
pp. 373-376 ◽  
Author(s):  
Kazuki Yoshihara ◽  
Masashi Kato ◽  
Masaya Ichimura ◽  
Tomoaki Hatayama ◽  
Takeshi Ohshima
Keyword(s):  
Electron Irradiation ◽  
Deep Level Transient Spectroscopy ◽  
Deep Level ◽  
Deep Levels ◽  
Low Energy ◽  
Epitaxial Layers ◽  
Before And After ◽  
Low Energy Electron ◽  
Transient Spectroscopy ◽  
P Type

We have characterized deep levels in as-grown and electron irradiated p-type 4H-SiC epitaxial layers by the current deep-level transient spectroscopy (I-DLTS) method. A part of the samples were irradiated with electrons in order to introduce defects. As a result, we found that electron irradiation to p-type 4H-SiC created complex defects including carbon vacancy or interstitial. Moreover, we found that observed deep levels are different between before and after annealing, and thus annealing may change structures of defects.

Characterization of CdS–CuInSe2 solar cells by current–voltage, capacitance–voltage, and capacitance-transient measurements

1987 ◽  
Vol 65 (8) ◽  
pp. 966-971 ◽  
Author(s):  
N. Christoforou ◽  
J. D. Leslie ◽  
S. Damaskinos
Keyword(s):  
Solar Cells ◽  
Deep Level ◽  
Current Voltage ◽  
Capacitance Voltage ◽  
Carrier Trap ◽  
Transient Spectroscopy ◽  
Increasing Temperature ◽  
P Type ◽  
Capacitance Transient ◽  
Transient Measurements

CdS–CuInSe2 solar cells, which have an efficiency of 9%, have been studied by current–voltage, capacitance–voltage, and capacitance-transient measurements over the temperature range 90–380 K. Deep-level transient spectroscopy analysis of the capacitance transient measurements reveals one majority carrier trap with an activation energy of 0.70 ± 0.02 eV. Although the present experiment cannot establish definitely if the trap is in the CdS or CuInSe2 layer, arguments are presented that it is a hole trap in the p-type CuInSe2 layer. Current–voltage measurements indicate a reversible increase in the reverse-bias leakage current with increasing temperature above 300 K. Evidence is presented that suggests that the rectifying barrier height in the CdS–CuInSe2 solar cell decreases rapidly with temperature above 300 K. Capacitance versus voltage measurements suggest that the depiction layer being studied is primarily in the CuInSe2, but the temperature dependence of the ionized charge concentration N(x) cannot be totally explained although one possible cause is suggested.

Deep Levels in As-Grown and Electron-Irradiated P-type 4H-SiC

2006 ◽  
Vol 911 ◽  
Author(s):  
Katsunori Danno ◽  
Tsunenobu Kimoto
Keyword(s):  
Cross Section ◽  
Deep Level Transient Spectroscopy ◽  
Capture Cross Section ◽  
Arrhenius Plot ◽  
Deep Level ◽  
Deep Levels ◽  
Emission Time ◽  
Transient Spectroscopy ◽  
P Type ◽  
Thermal Stability Of

AbstractDeep levels in as-grown and electron-irradiated p-type 4H-SiC have been investigated by deep level transient spectroscopy (DLTS). Three hole traps, namely HK2, HK3, and HK4, could be detected in the temperature range from 350K to 700K. Activation energies of the hole traps were estimated to be 0.84 eV for HK2, 1.27 eV for HK3, and 1.44 eV for HK4 from the Arrhenius plot of emission-time constants assuming temperature-independent capture cross section. By double-correlated DLTS (DDLTS), they were revealed to be donor-like (+/0) traps. The concentrations of HK3 and HK4 centers were clearly increased by low-energy (116 keV) electron irradiation. Based on thermal stability of the HK3 and HK4 centers up to 1350°C and the dependence of HK4 concentration on the electron fluence, they may originate from a complex including defect(s) caused by carbon displacement.

Deep Levels Generated by Ion-Implantation in n- and p-Type 4H-SiC

2009 ◽  
Vol 615-617 ◽  
pp. 365-368 ◽  
Author(s):  
Koutarou Kawahara ◽  
Giovanni Alfieri ◽  
Tsunenobu Kimoto
Keyword(s):  
High Temperature ◽  
Deep Level Transient Spectroscopy ◽  
Deep Level ◽  
Deep Levels ◽  
High Temperature Annealing ◽  
Implantation Damage ◽  
Transient Spectroscopy ◽  
P Type ◽  
Two Peaks ◽  
Dlts Spectra

The authors have investigated deep levels in the whole energy range of bandgap of 4H-SiC, which are generated by N+, P+, Al+ implantation, by deep level transient spectroscopy (DLTS). Ne+-implanted samples have been also prepared to investigate the pure implantation damage. In the n-type as-grown material, Z1/2 (Ec – 0.63 eV) and EH6/7 (Ec – 1.6 eV) are dominant deep levels. When the implant dose is low, seven peaks (IN1, IN3 ~ IN6, IN8, IN9) have emerged by implantation and annealing at 1000oC in the DLTS spectra from all n-type samples. After high-temperature annealing at 1700oC, however, most DLTS peaks disappeared, and two peaks, Z1/2 and EH6/7 survive. In the p-type as-grown material, D center (Ev + 0.40 eV) and HK4 (Ev + 1.4 eV) are dominant. When the implant dose is low, two peaks (IP1, IP3) have emerged by implantation and annealing at 1000oC, and four traps IP2, IP4 (Ev + 0.72 eV), IP7 (Ev + 1.3 eV), and IP8 (Ev + 1.4 eV) are dominant after annealing at 1700oC.

Thickness Dependence of Electronic Properties of GaN Epi-layers

1996 ◽  
Vol 449 ◽  
Author(s):  
W. Götz ◽  
J. Walker ◽  
L.T. Romano ◽  
N.M. Johnson ◽  
R.J. Molnar
Keyword(s):  
Hall Effect ◽  
Electronic Properties ◽  
Deep Level ◽  
Variable Temperature ◽  
Hall Effect Measurement ◽  
Interface Layer ◽  
Hydride Vapor Phase Epitaxy ◽  
Conduction Path ◽  
Hall Effect Measurements ◽  
Transient Spectroscopy

ABSTRACTThe electronic properties of heteroepitaxial GaN were investigated for unintentionally doped, n-type films grown by hydride vapor phase epitaxy on sapphire substrates. The GaN layers were characterized by variable temperature Hall-effect measurement, capacitance-voltage (C-V) measurements, and deep level transient spectroscopy (DLTS). The measurements were performed on as-grown, 13 μn thick films and repeated after thinning by mechanical polishing to 7 μm and 1.2 μm. The room temperature electron concentrations as determined by the Hall-effect measurements were found to increase from ∼1017 cm−3 (13 μm) to ∼1020 cm−3 (1.2 μm) with decreasing film thickness. However, the C-V and DLTS measurements revealed that the ionized, effective donor and deep level concentrations, respectively, remained unchanged in regions close to the top surface of the films. These findings are consistent with the presence of a thin, highly conductive near interface layer which acts as a parasitic, parallel conduction path. Possible sources of such a shunt near the GaN/sapphire interface include oxygen contamination from the sapphire substrate or a structurally highly defective, 300 nm thick interface layer.

Sign in / Sign up

Export Citation Format

Share Document