Investigation on the corrosive effect of NH3 during InGaN/GaN multi-quantum well growth in light emitting diodes

Abstract

Three series of samples with different NH3 flow rate are grown and the optical and structural properties are investigated. It is found that apart from a positive effect on keeping a high partial pressure of nitrogen to enhance indium incorporation, NH3 may also play a negative effect on indium incorporation during InGaN growth. Especially, when temperature is relatively high, the hydrogen generated from the dissociation of NH3 may suppress the chemical reaction which produces InN, leading to a reduced indium incorporation efficiency during the InGaN layer growth.

Reshaping of 3D GaN Structures during Annealing: Phenomenological Description and Mathematical Model

“…The decomposition rate of GaN generally increases when raising the partial pressure of hydrogen in the annealing chamber. ,, Conversely, it can be abated by adding ammonia since the radicals of this element can block the adsorption sites for nitrogen atoms to outgo the bulk. , While this is accurate in most of the cases, Koleske et al observed that the decomposition rate in a MOCVD reactor initially decreased with increasing NH 3 flux until reaching a minimum and then began to rise with further increasing ammonia partial pressure. This inflection in the trend is presumably related to a significant increase of hydrogen in the MOCVD chamber caused by the cracking of ammonia. ,, In accordance with Koleske et al, we observed a comparable trend in the decomposition rate for planar and microfin structures when increasing the ammonia flux from zero to 3800 sccm, as detailed in Table , C i . As shown in Figure a, the etching rate decreased drastically when adding 475 sccm of ammonia and increased slowly for planar and rapidly for microfins, raising the ammonia flux up to 3800 sccm.…”

Investigation into the MOCVD Growth and Optical Properties of InGaN/GaN Quantum Wells by Modulating NH3 Flux

“…For green InGaN/GaN MQW LDs, the incorporation of indium can be more sensitive to growth conditions due to the higher indium content in InGaN. For the samples in series I, the EL result corresponded well with results that have been previously reported [11,12]. However, a strange increase in the FWHM of the EL spectral peak (10~20 nm higher than other samples) was observed in sample B (grown at 2 slm NH3 flux), as shown in Figure 2c.…”

“…First, the wavelength of the EL peak increased when the NH 3 flow rate was below 2 slm during the InGaN layer growth, but the peak wavelength decreased with a further increase when the flow rate was over 2 slm, which indicated that the indium content in InGaN quantum wells decreases when the NH 3 flow rate is increased over a certain threshold, as shown in Figure 2b. Previous research has shown that NH 3 may have both positive and negative effects on the incorporation of indium atoms into InGaN quantum wells in the wavelength range of blue LED [11,12]. It has been reported that when InGaN is generated in MOCVD by NH 3 , TMIn, and TMGa, [13].…”

Facet Control and Material Redistribution in GaN Growth on Three-Dimensional Structures

“…This assumption may not seem intuitive, as it is widely known that the increase of ammonia flux generally hinders the decomposition of GaN when thermally annealed. − Furthermore, increasing its concentration while supplying gallium may increase the growth rate by preventing decomposition. , However, a decrease in the growth rate of GaN has also been reported when the flux of ammonia was increased beyond a certain value determined by the growth conditions, a phenomenon known as the site blocking effect. , Since the ammonia can occupy nitrogen and gallium adsorption sites, it may prevent the incorporation of gallium when the concentration is too high. Besides, one should also consider the corrosive effect that NH 3 may have during growth due to the release of hydrogen when the molecule is dissociated, especially under nitrogen-rich atmospheres. , Based on the previous statements, it would be reasonable to assume that at high temperatures, high ammonia fluxes can promote the decomposition process and thus reduce the growth rate of the polar surface provided that a nonpolar plane is in close vicinity. Consequently, the etching of the c- plane observed on the microfins and the formation of semipolar facets are determined not by the V/III ratio but rather the partial pressure of ammonia.…”

“…Besides, one should also consider the corrosive effect that NH 3 may have during growth due to the release of hydrogen when the molecule is dissociated, especially under nitrogen-rich atmospheres. 51,52 Based on the previous statements, it would be reasonable to assume that at high temperatures, high ammonia fluxes can promote the decomposition process and thus reduce the growth rate of the polar surface provided that a nonpolar plane is in close vicinity. Consequently, the etching of the c-plane observed on the microfins and the formation of semipolar facets are determined not by the V/III ratio but rather the partial pressure of ammonia.…”