Influence of growth kinetics on the indium distribution during MOVPE growth of GaInN quantum wells

Abstract

The composition and thickness of GaInN quantum wells (QWs) determines the luminescence properties of GaInN/GaN-based optoelectronic devices. The In distribution is characterized by considerable inhomogeneities on two spatial scales. Variations of locally averaged In concentrations and QW thickness on a "large" scale of several 10 nm along the QW occur in addition to small clusters with high In concentrations up to 100% and sizes of only a few nanometers. In the present work, we investigated the influence of the growth rate during metal organic vapor phase epitaxy (MOVPE) growth on the In distribution. The composition of GaInN single QWs was determined by evaluating high-resolution transmission electron microscopy (HRTEM) lattice-fringe images. At low GaInN deposition rates, a significant increase of the inhomogeneity of the In distribution compared to a sample grown with a high rate was found. A good correlation between experimental and calculated photoluminescence energies is achieved. 1 Introduction Enormous progresses regarding the growth of group-III nitrides by metalorganic vapor phase epitaxy (MOVPE) were achieved in the past years and commercial GaInN-based light emitting diodes (LEDs) and laser diodes (LDs) have been realised [1]. However, the effect of different mechanisms -phase separation, In segregation and In desorption -during the epitaxial growth of GaInN quantum wells (QWs) are still not understood well enough to control precisely the In distribution. GaInN QWs have been shown to contain pronounced composition fluctuations, in particular small In-rich clusters (<5 nm) [2,3], which can be attributed to phase separation due to the large miscibility gap of InGaN [4]. These In-rich clusters have been suggested to dominate the photoluminescence (PL) of InGaN QWs by acting as quantum dots by O'Donnell et al. [5]. With respect to the development of LDs in the blue/green spectral range, which can be achieved in principle by structures containing quantum dots with suitable size and In concentration, a good understanding of the effects dominating the growth mode, the average composition and In distribution in GaInN QWs is required. In the present work, the influence of the growth rate during MOVPE growth on the In distribution of GaInN single QWs was investigated. The measured In concentrations and QW thicknesses were correlated with room-temperature PL spectra.

Important interaction effects in the growth of InGaN violet light emitting diodes by MOCVD

“…The small interaction between Ga flow rate and temperature can be seen as a kink in the plane for the graph in Figure 3a It is well known that the growth temperature and Ga flow rate will affect the emission wavelength of InGaN based layers 18 , however the interaction between the two has not been studied previously. The effect of the growth kinetics on the indium distribution in InGaN quantum wells was studied previously 19 and it was found that there is a large effect of the growth rate on the In distribution inside the well. At lower growth rates there is a higher degree of long range clustering of In atoms, but that the size of small agglomerates was not affected.…”

Microstructure of III‐N semiconductors related to their applications in optoelectronics

“…There is many contradictory experimental data on Insegregation in InGaN quantum wells. From our experience and the works of Hahn et al [16], we can issue a list of the main obstacles, why the task of growing uniform InGaN quantum wells is so difficult:…”