Sources of carrier compensation in metalorganic vapor phase epitaxy-grown homoepitaxial n-type GaN layers with various doping concentrations

Physica Status Solidi (a)

Chen

et al. 2021

The development of high‐quality gallium nitride (GaN) epitaxy with thick drift layer, low controllable doping, and high mobility is key for vertical high‐power devices. Herein, the effect of increasing trimethylgallium (TMGa) molar flow rate on the growth rate, impurity incorporation, charge compensation, surface morphology, and carrier mobility is systematically studied. An optimized metalorganic chemical vapor deposition GaN growth condition with a typical growth rate of 2 μm h−1 is used as the baseline. With significant suppression of background Si, other impurity concentrations, and a precise control of the doping precursor SiH4 flow, an electron concentration as low as 4 × 1015 cm−3 in n−‐GaN is achieved. Through increasing the TMGa flow rate, the GaN growth rate is increased to 5.2 μm h−1. Secondary ion mass spectroscopy results show that the background H, O, and Mg remain below detection limit, but C level is increased to 2 × 1016 cm−3. GaN growth on Mn‐doped semi‐insulating GaN substrate is performed to probe the transport properties of film with low dislocation densities. Hall measurement shows that an electron mobility decreases from 852 to 604 cm2 V−1 s−1 as the growth rate increases. Results from this work reveal the challenge and guidance for achieving GaN vertical high power devices.

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Metalorganic Chemical Vapor Deposition Gallium Nitride with Fast Growth Rate for Vertical Power Device Applications

Physica Status Solidi (a)

Chen

et al. 2021

Physica Status Solidi (b)

“…In all of the spectra, a large dominant peak appears at approximately 270 K. For both samples, the peak height depends on the off‐angle. Deep‐level defects in n‐GaN crystals have been intensively studied by DLTS measurements and have been identified as E1 ( E C − 0.24–0.26 eV), E2 ( E C − 0.40 eV), and E3 ( E C − 0.57–0.61 eV) in this temperature range . The E2 defect is typically not detected in GaN epitaxial layers grown on GaN substrates.…”

Section: Resultsmentioning

confidence: 99%

Effect of Wafer Off‐Angles on Defect Formation in Drift Layers Grown on Free‐Standing GaN Substrates

Shiojima

Horikiri

Yoshida

et al. 2019

The effect of the surface off‐angle toward either the a‐ or m‐axis on the defect formation is characterized using deep‐level transient spectroscopy (DLTS) in conjunction with the carrier concentration for Ni Schottky contacts formed on n‐GaN drift layers. In both noncontact and conventional capacitance–voltage results, off‐angle dependence on carrier concentration is observed. For all samples, a large dominant peak appears at approximately 270 K in the DLTS spectra and is attributed to E3 (EC − 0.57–0.61 eV) defects. Carbon atoms can act as carrier compensators and form E3 defects. These results can be interpreted based on how C incorporation during crystal growth depends on the off‐angle.

“…As compared with previous reports, the LA-MOCVD GaN growth achieved low [C] at mid-10 15 cm À3 with the lowest input V/III ratio/GR. versus input V/III ratio of MOCVD GaN from the literature [2,9,13,14,32,[35][36][37][38][39][40] and from this study. b) [C] versus input V/III ratio/GR of MOCVD GaN from the literature [2,9,13,14,32,37,39,40] and from this study.…”

Section: Impurity Incorporationmentioning

confidence: 99%

“…The GRs of conventional MOCVD and LA-MOCVD samples were 5.2 and 4.5 μm h À1 , respectively. b) Hall mobility versus electron concentration of GaN grown with HVPE, MBE, and MOCVD on various substrates from the literature,[2,3,32,35,[41][42][43][44][45] and LA-MOCVD samples from this study. The reported GRs from the literature are listed in the table.…”

mentioning

confidence: 99%

Laser‐Assisted Metal–Organic Chemical Vapor Deposition of Gallium Nitride

Chen

Physica Rapid Research Ltrs

et al. 2021

Ammonia (NH3) is commonly used as group‐V precursor in gallium nitride (GaN) metal–organic chemical vapor deposition (MOCVD). The high background carbon (C) impurity in MOCVD GaN is related to the low decomposition efficiency of NH3, which represents one of the fundamental challenges hindering the development of high‐purity thick GaN for vertical high‐power device applications. This work uses a laser‐assisted MOCVD (LA‐MOCVD) growth technique to address the high‐C issue in MOCVD GaN. A carbon dioxide (CO2) laser with a wavelength of 9.219 μm is utilized to facilitate NH3 decomposition via resonant vibrational excitation. The LA‐MOCVD GaN growth rate (GR; as high as 10 μm h−1) shows a strong linear relationship with the trimethylgallium (TMGa) flow rate, indicating high effective V/III ratios and, hence, efficient NH3 decomposition. [C] in LA‐MOCVD GaN films decreases monotonically, as the laser power increases. A low [C] at 5.5 × 1015 cm−3 is achieved in the LA‐MOCVD GaN film grown with GR of 4 μm h−1. LA‐MOCVD GaN films reveal high crystalline quality with room‐temperature mobility of >1000 cm2 V−1 s−1. LA‐MOCVD provides an enabling route to achieve high‐quality GaN epitaxy with low‐C and fast GR simultaneously. This technique can be extended for epitaxy of other nitride‐based semiconductors.