Influence of template type and buffer strain on structural properties of GaN multilayer quantum wells grown by PAMBE, an x-ray study

Abstract

The influence of template type and residual strain of the buffer layer on the structural properties of GaN/AlN superlattices (SLs) was studied using high resolution x-ray diffraction. Using sapphire substrates, an effective thinning of the GaN quantum wells and the corresponding thickening of the AlN barriers were observed in SL structures grown on thin, strained AlN templates as compared with SL structures grown on thick, relaxed GaN templates. Moreover, a bimodal strain relaxation of SL structures in dependence of template type was observed. The SLs grown on AlN templates relax predominantly by the formation of misfit dislocations, while the SLs grown on GaN templates relax predominantly by cracking of the layers. We explain these effects by the influence of residual strain in the buffer/template systems used for the growth processes of SL layers. A correlation is made between the strain state of the system and the cracking processes, the dislocation density, the radius of curvature and the layer thickness.

Substrate effects on the strain relaxation in GaN/AlN short-period superlattices

“…This can be explained by thermally activated and strain-depended exchange between the Al ad-atoms and the Ga atoms from the GaN SL layers. This is described in detail in [17,18]. …”

New Silicon Magnetic Field Sensor

“…Ціми проблемами є: (1) наявність високих концентрацій власних дефектів і зовнішніх домішок у AlGaN, які можуть знизити ефективність опто-електронних приладів, і (2) різниця темпів при одночасному зростанні ІІІ-та N-полярними поверхнями. Незважаючи на значний експериментальний матеріал, що накопичений на теперішній час [5][6][7], адекватних моделей, що пояснюють процес формування плівок AlGaN не існує. Для їх створення важливе теоретичне вивчення станів зростаючої плівки.…”

The Peculiarities of Strain Relaxation in GaN/AlN Superlattices Grown on Vicinal GaN (0001) Substrate: Comparative XRD and AFM Study

“…However, a minimization of strain relaxation by growth of both GaN and AlN under Ga excess conditions was shown for GaN/AlN (1.5/3 nm) SLs grown on both AlN- and GaN-on-sapphire templates [5]. A bimodal strain relaxation of GaN/AlN short-period SL structures independent of the type of template (GaN-thick- or AlN-thin-on-sapphire) was observed in [8, 9]. This is contrasted by the data presented in [10], which unambiguously demonstrates that the structural quality of a 10-period GaN/AlGaN SL is limited by the structural properties of the GaN substrate.…”