Interplay between the growth temperature, microstructure, and optical properties of GaInNAs quantum wells

Abstract

We investigated the influence of the growth temperature (Tgr) on the microstructure and on the optical properties of GaInNAs quantum wells (QWs). By comparing the structural information (transmission electron microscopy) with the optical properties (photoluminescence spectroscopy), we demonstrate that high photoluminescence efficiency of GaInNAs QWs is achieved only when the two-dimensional growth mode is preserved, which can be obtained at a low Tgr even for high In content. We also show composition modulations in the GaInNAs QWs, which can lead to the interface roughness.

Structural properties of GaAsN∕GaAs quantum wells studied at the atomic scale by cross-sectional scanning tunneling microscopy

“…Nevertheless, the optical emission of ͑In͒GaAsN / GaAs quantum wells ͑QWs͒ showed typically a strong degradation when the N content is increased. [1][2][3] This has been frequently attributed to different phenomena, such as N being incorporated in interstitial positions, 4,5 compositional fluctuations in the alloy, [6][7][8] or a rough top interface. 8 All these have motivated a strong effort in the last years on the structural characterization of ͑In͒GaAsN alloys, but only very few of these studies were performed using cross-sectional scanning tunneling microscopy ͑X-STM͒.…”

“…[1][2][3] This has been frequently attributed to different phenomena, such as N being incorporated in interstitial positions, 4,5 compositional fluctuations in the alloy, [6][7][8] or a rough top interface. 8 All these have motivated a strong effort in the last years on the structural characterization of ͑In͒GaAsN alloys, but only very few of these studies were performed using cross-sectional scanning tunneling microscopy ͑X-STM͒. [9][10][11] This technique is very useful because it allows to image the cross section of a QW or bulk layer with atomic resolution and distinguish between the different atoms in the alloy.…”

“…This is in agreement with what was found for MOVPE grown GaAsN alloys with 1.7% N. 9,10 The short and long range compositional fluctuations observed in GaInNAs/ GaAs QWs with similar N contents are not present in this case. 7,8 Figure 2 shows a high resolution filled states image of all the different N-related features found. The darkest spots labeled A are N As substitutional impurities in the surface plane ͑first atomic layer͒.…”

InAs quantum dot morphology after capping with In, N, Sb alloyed thin films

“…The presence of one element can influence the incorporation and the spatial distribution of the other. 16,17 All three mechanisms (strain driven mass transport, surface diffusion, phase separation) should strongly affect the electronic structure and optical properties of the QDs. To fully exploit the possible advantages of the different capping materials and the above mechanisms, a deeper knowledge of the final QD/capping layer morphology is needed.…”

MBE growth and interface formation of compound semiconductor heterostructures for optoelectronics

“…Our careful analysis of the (Ga,In)(N,As) microstructure and local composition in these QWs has shown that, as demonstrated above for Ga(As,N), the 2D-3D transition is not related to the lattice mismatch but to the inherent phase instability. In fact, a recent analysis of 2D grown (Ga,In)(N,As) QWs by spatially resolved electron energy-loss spectroscopy has demonstrated that this instability of the metastable alloy is driven by a maximization of the cohesive bond energies of the corresponding adatoms [15]. In addition, the best optoelectronics properties are obtained with these systems when perfect 2D interfaces are formed.…”