Connection between Carbon Incorporation and Growth Rate for GaN Epitaxial Layers Prepared by OMVPE

Abstract

Carbon, a compensator in GaN, is an inherent part of the organometallic vapor phase epitaxy (OMVPE) environment due to the use of organometallic sources. In this study, the impact of growth conditions are explored on the incorporation of carbon in GaN prepared via OMVPE on pseudo-bulk GaN wafers (in several cases, identical growths were performed on GaN-on-Al2O3 templates for comparison purposes). Growth conditions with different growth efficiencies but identical ammonia molar flows, when normalized for growth rate, resulted in identical carbon incorporation. It is concluded that only trimethylgallium which contributes to growth of the GaN layer contributes to carbon incorporation. Carbon incorporation was found to decrease proportionally with increasing ammonia molar flow, when normalized for growth rate. Ammonia molar flow divided by growth rate is proposed as a reactor independent predictor of carbon incorporation as opposed to the often-reported input V/III ratio. A low carbon concentration of 7.3 × 1014 atoms/cm3 (prepared at a growth rate of 0.57 µm/h) was obtained by optimizing growth conditions for GaN grown on pseudo-bulk GaN substrates.

Characterization of As-Grown and Regrown GaN-on-GaN Structures for Vertical p-n Power Devices

“…Moreover, these defects would act as sites for Mg precipitation within p-GaN and contribute to decreased electrical conductivity and increased onresistance. 24 In comparison, the multiply etched devices easily achieved reverse bias of 1kV without breakdown. Thus, it was clear that the etchinginduced damage, rather than Mg precipitates in the p-GaN layer, had contributed to the early device breakdown.…”

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

“…This factor can be considered from the GaN film GR, considering that [C] is positively related to the GaN GR. [14,32] Therefore, [C] is plotted as a function of the input V/III ratio/ GR from this work as compared with the data reported from the literature, as shown in Figure 7b. The dashed line indicates the slope of [C] versus input V/III ratio/GR for the best reported data, considering that [C] is reversely proportional to V/III ratio and 1/GR.…”

“…Thus, the GaN GR is limited by the mass transport of Ga species, i.e., the TMGa flow, and, therefore, has a linear relationship with the TMGa flow rate. [14] As the TMGa flow rate increases, the effective V/III ratio decreases, which can lead to nonlinear relationship between the GR and the TMGa flow rate due to the limited N species. Figure 3 shows the GaN GR as a function of the TMGa flow rate under different input laser power: 0 (without laser), 150, and 250 W. The chamber pressure was fixed at 150 Torr, and NH 3 flow was kept at 4 slm.…”

“…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.…”

“…Theoretical investigations suggested that the high effective V/III ratio is an effective approach to reduce C incorporation. [10,11] Conventional approaches to suppress C incorporation in MOCVD GaN growth include: 1) increasing input V/III ratio via increasing NH 3 flow or decreasing TMGa flow [2,9,[12][13][14][15] ; 2) increasing growth pressure [9,12,15] ; and DOI: 10.1002/pssr.202100202 Ammonia (NH 3 ) 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 NH 3 , which represents one of the fundamental challenges hindering the development of high-purity thick GaN for vertical high-power device applications.…”