Selectivity enhancement by hydrogen addition in selective area metal‐organic vapor phase epitaxy of GaN and InGaN

Abstract

Selective area metal-organic vapor phase epitaxy (SA-MOVPE) allows in-plane control of layer composition and thickness. The use of relatively wide (>10 mm) selective masks brings about large wavelength modulation, taking advantage of vapor-phase diffusion of precursors. The wide masks, however, tend to induce nucleation on them, leading to much reduced and uncontrollable wavelength modulation. To obtain deposition selectivity between masks and crystal surface, hydrogen addition was proved to be effective by preventing GaN nucleation on masks. Consequently, the maximum growth rate enhancement of 4.8 and the photoluminescence peak shift of 54 nm (nominally 11% shift in the indium composition) were achieved for InGaN bulk layer.

Analysis of the Gas Phase Kinetics Active during GaN Deposition from NH3 and Ga(CH3)3

“…Equilibrium calculations were performed by minimizing the Gibbs free energy of the system assuming a pressure of 0.2 bar and initial mole fractions of 0.25 for NH 3 , 0.7495 for H 2 and 5.0 × 10 –4 for Ga­(CH 3 ) 3 . These conditions correspond to those often adopted to deposit high quality GaN films. ,− Simulations were performed in the 700–1500 K temperature range. The results are reported in Figure a, for GaXYZ species (with X,Y, Z either CH 3 , NH 2 , or H), CH 4 , NH 3 , and H 2 , in Figure b for species containing 2 or 3 Ga atoms, and in Figure c for the decomposition fragments of the growth precursors.…”

“…The gas phase reactivity was investigated embedding the kinetic mechanism described in section into a 2D model of the single wafer horizontal reactor AIX200/4, which has been often used to deposit GaN nitride thin films. − A sketch of the reactor configuration is shown in Figure , while the simulated temperature profile is reported in Figure . Simulations were performed assuming that GaNH 2 decomposes upon collision with the surface to give GaN and H 2 .…”

“…The preferred industrial method to produce such material is metal organic vapor phase epitaxy (MOVPE), using ammonia and trimethyl gallium (TMGa) as gaseous precursors . At the typical operative conditions for the GaN growth, it is generally agreed that the deposition rate is controlled by the diffusion of the growth precursors, − because at the elevated temperatures (1200–1400 K) at which GaN is deposited surface reactions are generally fast. The gas phase kinetics active during GaN deposition plays an important role as it is responsible for producing the precursors to the GaN growth, as well as because its control is necessary in order to limit the formation of powders. ,− This side reactivity is strongly undesired because these powders scavenge part of the precursors, limiting the deposition rate.…”

“…At the typical operative conditions for the GaN growth, it is generally agreed that the deposition rate is controlled by the diffusion of the growth precursors, − because at the elevated temperatures (1200–1400 K) at which GaN is deposited surface reactions are generally fast. The gas phase kinetics active during GaN deposition plays an important role as it is responsible for producing the precursors to the GaN growth, as well as because its control is necessary in order to limit the formation of powders. ,− This side reactivity is strongly undesired because these powders scavenge part of the precursors, limiting the deposition rate. Also, if they reach and get adsorbed on the substrate, they can considerably affect the quality of the film, because of the inclusion of additional defects to the crystalline layer and as they can lead to deposition outside of the desired growth areas.…”

Directly correlated microscopy of trench defects in InGaN quantum wells

“…Regarding SAE, Shioda et al showed emission wavelengths from near-mask-edge regions of SAE-grown InGaN were longer for wider mask widths. However, their masks were 10s of µm wide 42 , so these diffusion-controlled effects may not apply on the significantly smaller length scales masked by the open trenches.…”