Effects of Carrier Gas on Carbon Incorporation in GaN

Abstract

GaN epitaxial layers were grown on Si (111) substrates by metal organic chemical vapor deposition. Carbon concentrations in the films grown in different ambients were measured by secondary ion mass spectrometry. The results show that the carbon incorporation is strongly dependent on the H2 flow rate when the NH3 flow rate is small, but insensitive to the H2 flow rate when the NH3 flow rate is sufficient large. We conclude that H2 can inhibit the dissociation of NH3 and result in a less active N source; an insufficiently active N source causes more N vacancies, which enhances carbon incorporation.

Progress in Modeling Compound Semiconductor Epitaxy: Unintentional Doping in GaN MOVPE

“…This is due to the change in p MMg eq / p Ga eq ratio, i.e., the MMG/GaH supply ratio, as shown in Figure b. The tendency agrees with the experimental results − (Table ). On the other hand, the ρ C ,surface value on GaN(0001) is lower than that of GaN(000–1).…”

“…Figure b shows the carbon concentration in the bulk as a function of temperature. The tendencies deduced reproduce the experimental results − shown in Tables and , where the carbon concentration decreases with increases in temperature, decreases with the V/III ratio, and in the case of GaN(0001) growth, is higher than that in the case of GaN(000–1). These results imply the feasibility of the integrated model.…”

“…(b) Carbon concentration in the bulk as a function of temperature. The tendencies agree well with the results of experiments − shown in Tables and .…”

“…In GaN MOVPE, the C atoms come from TMG, which contains a methyl group. Several studies have investigated the relationships between growth conditions and C concentrations in GaN. − These experiments have determined the following: C concentrations decrease with (1) increases in growth temperature, , (2) increases in NH 3 partial pressure, − and (3) decreases in TMG partial pressure. ,,, Tendencies 2 and 3 suggest that C concentrations decrease with increases in the V/III ratio. Furthermore, C concentrations in GaN grown along the [0001] direction are higher than those along the [000–1] direction. ,, These tendencies are summarized in Table .…”

Control of impurity concentration in N‐polar () GaN grown by metalorganic vapor phase epitaxy

“…This is mostly due to the incorporation of high‐density impurities in N‐polar epilayers. There are many reports that N‐polar GaN includes higher amounts of oxygen than Ga‐polar GaN . Oxygen acts as a shallow donor.…”