Atomic-Scale Insights into the Interfacial Polarization Effect in the InGaN/GaN Heterostructure for Solar Cells.

The model system of the InGaN/GaN quantum wells (QWs), based on the first principles calculation, was chosen to understand the underlying mechanism of interfacial polarization and its synergic effect with the built-in electric field (Bef) at the p-n junction in solar cells (SLs). The polarized electric field (Pef) was generated due to the redistribution of electrons and holes at the interface; moreover, the Pef of InGaN/GaN heterostructure on the semipolar (01-11) GaN surface was consistent with that of on the N-polar (000-1) surface, which is on the lines of the Bef and favors the electron-hole separation efficiency in SLs. Furthermore, the growth of high-quality InGaN/GaN QWs on the semipolar (01-11) GaN surface was achieved. Such an atomic-scale investigation provides a fundamental understanding of the polarization charge-induced Pef and its interaction coupling with Bef at the p-n junction, which could be generalized to polar material-based SLs.

A partly-contacted epitaxial lateral overgrowth method applied to GaN material.

We have discussed a new crystal epitaxial lateral overgrowth (ELO) method, partly-contacted ELO (PC-ELO) method, of which the overgrowth layer partly-contacts with underlying seed layer. The passage also illustrates special mask structures with and without lithography and provides three essential conditions to achieve the PC-ELO method. What is remarkable in PC-ELO method is that the tilt angle of overgrowth stripes could be eliminated by contacting with seed layer. Moreover, we report an improved monolayer microsphere mask method without lithography of PC-ELO method, which was used to grow GaN. From the results of scanning electron microscopy, cathodoluminescence, x-ray diffraction (XRD), transmission electron microscopy, and atomic force microscope (AFM), overgrowth layer shows no tilt angle relative to the seed layer and high quality coalescence front (with average linear dislocation density <6.4 × 10(3) cm(-1)). Wing stripes peak splitting of the XRD rocking curve due to tilt is no longer detectable. After coalescence, surface steps of AFM show rare discontinuities due to the low misorientation of the overgrowth regions.