Laser-Assisted Reactivity of Triethylgallium or Trimethylgallium with Ammonia in Constrained Pulsed Nozzle Expansions

Abstract

The results of laser-assisted reactivity in constrained gas expansions involving either triethylgallium (TEGa) or trimethylgallium (TMGa) with ammonia are reported. NH3 (or ND3) along with TEGa or TMGa are introduced into a high vacuum chamber through a customized dual-source pulsed nozzle assembly. Excimer laser output (193 or 248 nm) is focused into the mixing and reaction region of the nozzle source, and a quadrupole mass spectrometer interrogates the photolyzed expansion. During gas mixing and expansion into the vacuum, the adduct signals from TMGa:NH3 or TEGa:NH3 are observed when the nozzle assembly is cooled. Laser irradiation of the gas mixtures results in the formation of new adducts, TMGa:NH2 or TEGa:NH2, and diverse, higher mass GaN-containing species. Power and wavelength dependence studies are used to reveal the photolytic origins of individual mass spectral features, and the influence of sample pressure on cluster formation processes is also examined.

DFT Modeling of Chemical Vapor Deposition of GaN from Organogallium Precursors. 2. Structures of the Oligomers and Thermodynamics of the Association Processes

“…According to our calculations, hexameric [MeGaNH] 6 cluster is the most stable gas-phase molecule in the GaMe 3 -NH 3 system below 935 K. Very recently dimeric clusters have also been observed in the gas phase in the temperature interval 300-1000K. 26 However, experimental setup was able to detect masses up to 240 26 or 300 23 amu, and from the obtained data it is not clear if the largest mass observed at 217 amu [ascribed to Me 3 HGa 2 (NH 2 )NH + ] 23 and 234 amu [ascribed to Me 4 Ga 2 (NH 2 ) 2 + ] 26 result from the dimer or from some heavier GaN containing species. It is very important to note that the relative MS intensity of the cluster compounds in the gas phase is increasing under laser irradiation (the main objective of which is to assist N-H bond breaking).…”

“…Our thermochemical analyses suggest that the whole series of [R x GaNR′ x ] n compounds may exist in the gas phase. In their recent paper on the laser-assisted MOCVD of GaN under high pressure-low temperature (well below room temperature) conditions, Koplitz and co-workers 23 identified the formation of a new TMG-NH 2 adduct, "and diverse, higher mass GaN-containing species". According to our calculations, hexameric [MeGaNH] 6 cluster is the most stable gas-phase molecule in the GaMe 3 -NH 3 system below 935 K. Very recently dimeric clusters have also been observed in the gas phase in the temperature interval 300-1000K.…”

Materials Chemistry of Group 13 Nitrides

“…In contrast to this, in-depth analyses of the surface chemistry (based on experimental and computational data) associated with the growth of the nitrides are still almost absent, in particular for GaN and InN. However, information on the (related) gas-phase chemistry recently became available [53][54][55]. The gas-phase composition of the Me 3 Ga/NH 3 Scheme 1 Cleavage of three M -C bonds per precursor molecule using conventional precursors MR 3 and NH 3 system close to the substrate was monitored as a function of the substrate temperature using a molecular beam sampling technique and quadrupole mass spectrometry as well as REMPI spectroscopy [137].…”

Effect of Growth Pressure and Gas-Phase Chemistry on the Optical Quality of InGaN/GaN Multi-Quantum Wells

“…Current production-level LED structures are typically grown at low-pressure conditions for the MQW active region ( 200 Torr), where the reactor designs can maintain extremely reproducible and uniform performance. However, there have been limited reports on the chemical mechanisms that occur during the InGaN OMVPE process [1,[3][4][5][6] and the process optimization needed to achieve high quality material. Of particular interest is the effect that growth pressure has on the optical and morphological properties of the InGaN material.…”