Built‐in fields in non‐polar In_xGa_1–xN quantum dots

Abstract

We present a detailed analysis of the internal built‐in potential in polar and non‐polar Inx Ga1–x N quantum dots (QDs). The applied model is based on a surface integral method to calculate the three‐dimensional electrostatic built‐in potential in semiconductor QDs of arbitrary shape. This technique allows for a detailed and systematic analysis of the different contributions to the total built‐in field. Here, we also investigate the impact of the QD geometry on the built‐in potential in structures grown along non‐polar directions of the crystal.Since there is uncertainty in the literature as to the sign of the piezoelectric constant e15 associated with the shear strain, we study the influence of this constant in detail. While recent results on non‐polar GaN/AlN QDs indicate that only a negative e15 leads to significant reduction in the built‐in field, we show that for InN/GaN QDs there should still be a significant field present, independent of the sign of the piezoelectric constant e15. However, this field is strongly reduced with increasing Ga concentration in the nanostructure. (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Prediction of strong ground state electron and hole wave function spatial overlap in nonpolar GaN/AlN quantum dots

“…3 The electrostatic built-in field and its impact on the electronic and optical properties have been studied theoretically. 6,8,9 The properties of a-plane GaN/AlN QDs have been discussed in Ref. 6.…”

“…Their geometrical features deviate significantly from the previously assumed truncated pyramidal or lens-shaped QD shapes. 6,8,9 To date no detailed analysis of the built-in field, the electronic, and the optical properties has been performed for arrowhead-shaped structures. Therefore, the aim of this work is to present a detailed analysis of realistic arrowhead- shaped a-plane GaN/AlN QDs.…”

“…First, we have shown that for nonpolar In x Ga 1Àx N/GaN dots, with In contents of 5%-35%, the builtin field vanishes almost completely and one is left with a negligible potential difference between the QD facets along the c-axis. 8 Therefore, a high spatial overlap of electron and hole wave functions is expected. This prediction was recently confirmed by an experimental study 14 high-energy electron diffraction, high-resolution transmission electron microscopy and scanning electron microscopy], revealed an even more precise picture of the dot geometry.…”

A study of the piezoelectric properties of semipolar 112̅2 GaN/AlN quantum dots

“…Recent work has demonstrated active III‐nitride semipolar light‐emitting diodes and lasers in the green and blue region of the spectrum . Analysis of the internal built‐in polarization potential of nonpolar InGaN/GaN QDs showed strong reduction with increasing Ga content (). Comparison between polar and semipolar InGaN/GaN QDs showed blue‐shifted emission of the PL for the semipolar nanostructures compared to the polar ones, but this was attributed to lower indium incorporation in the semipolar case ().…”

Formation of m-plane InGaN/GaN quantum dots using strain engineering of AlGaN/AlN interlayers

“…7 Theoretical work has shown that the QCSE can be nearly eliminated in nonpolar InGaN QD systems with lower In concentration. 8 Furthermore, nonpolar and semipolar nitride systems can exhibit other interesting properties such as the larger exciton binding energy compared with the polar systems. 9,10 Therefore, it is desirable to grow InGaN QDs on the nonpolar and semipolar surfaces.…”