Quantum chemical mechanism in parasitic reaction of AlGaN alloys formation

Computational fluid dynamics on gaseous and surface chemistry of GaN‐MOVPE system for various pressures

“…[11][12][13][14][15][16], we have constructed the reaction pathways in MOVPE-GaN growth, as shown in Fig. 2.…”

“…Notice, here, that the only case of n = 1 in (v) can contribute to (DMG:NH 2 ) 2 (dimer) formation in (ii). In adduct formation, CH 4 separation is considered as an irreversible reaction while NH 3 trading is of reversible, due to an activation energy difference [11][12][13]. The generation of huge molecules in the case of (iv) and (v) can be related to the nano-particle formation [17].…”

Quantum chemical study on substituent effect of gas‐phase reactions in III–V nitride semiconductor crystal growth

“…2, and the relative energies of the reaction species are listed in Table 2. Similarly as for R = CH 3 and C 2 H 5 in the previous papers [9][10][11][12][13][14], both the activation energy and the heat of reaction for the Al source system are lower than those for the Ga source system in reaction (2). The relative energies of 3a and 3g are respectively lower than those of corresponding amino adducts for R = CH 3 and C 2 H 5 because the M-N interaction in MR 2 NH 2 is not the coordination interaction but the covalent bond where the strength of interaction is affected seriously by the ability for electron donation due to alkyl groups, and therefore the stronger M-N interaction for R = t-C 4 H 9 reduces the relative energies of 3 more remarkably according to the same reason that the stronger Al-N interaction in the Al source system reduces the heat of reaction more strikingly.…”

“…On the other hand, the growth of AlGaN layers at atmospheric-pressure MOVPE is inhibited by gas-phase reactions among precursors leading to adduct formation, called "parasitic reactions" [3 -5]. We have studied the mechanism of gas-phase reactions in MR 3 /H 2 /NH 3 (M = Al, Ga, In; R = CH 3 , C 2 H 5 ) systems by a quantum chemical approach [9 -17], and have clarified that the Al source gases and their deviates enhance reactivity to the parasitic reactions [9][10][11][12][13][14]. In order to suppress the parasitic reactions, we have to consider another Al source gas for the growth of AlGaN.…”

Multiwafer atmospheric‐pressure MOVPE reactor for nitride semiconductors and ex‐situ dry cleaning of reactor components using chlorine gas for stable operation

“…The particular challenge in controlling the growth process lies in the occurrence of parasitic reactions between the metalorganic source materials and NH 3 leading to the formation of low volatility adduct species and subsequent gas-phase nucleation. We have been studying vapor-phase reaction of organometallics and NH 3 experimentally and by quantum chemical analysis [3,4] To the best of our knowledge, there are no reports the effects of growth pressure on both AlGaN and Mg-doped GaN in the pressure range from 300 Torr to 760 Torr in the same reactor; at these pressures, significant parasitic reactions between organometals and NH 3 begin to occur [5]. It is believed that group-III reactants are removed from the gas flow by this mechanism, which thus affects the GaN growth efficiency.…”