X-ray Reciprocal Space Mapping of Graded Al x Ga1 - x N Films and Nanowires.

Hryhorii V Stanchu,Morgan E Ware,Zbigniew R Zytkiewicz,Alexander E Belyaev,Yuriy I Mazur,Andrian V Kuchuk,Vasyl P Kladko,Gregory J Salamo

doi:10.1186/s11671-016-1299-7

Abstract

The depth distribution of strain and composition in graded AlxGa1 − xN films and nanowires (NWs) are studied theoretically using the kinematical theory of X-ray diffraction. By calculating left(20overline{2}5right) reciprocal space maps (RSMs), we demonstrate significant differences in the intensity distributions from graded AlxGa1 − xN films and NWs. We attribute these differences to relaxation of the substrate-induced strain on the NWs free side walls. Finally, we demonstrate that the developed X-ray reciprocal space map model allows for reliable depth profiles of strain and Al composition determination in both AlxGa1 − xN films and NWs.

Highlights

The demonstration of p-type doping through the socalled polarization doping technique for AlxGa1 − xN alloys is finding more and more practical applications in modern optoelectronic devices
It is well known that epitaxial films of III-nitrides grow in columnar structures of relatively perfect material bounded by dislocation arrays
The fitting of an experimental asymmetrical reciprocal space maps (RSMs) will allow for the separation of strain, composition, and structural parameters in graded AlxGa1 − xN films and NWs

Summary

Introduction

The demonstration of p-type doping through the socalled polarization doping technique for AlxGa1 − xN alloys is finding more and more practical applications in modern optoelectronic devices. Using compositionally graded AlxGa1 − xN films, polarization-induced p-n junctions and light emitting diodes (LEDs) have been successfully fabricated [1,2,3] This fundamentally new type of p-n junction allowing deep ultraviolet LEDs was shown for graded AlxGa1 − xN catalyst-free nanowires (NWs) without the use of impurity doping [4, 5]. Such doping enhancement occurs from grading the composition of AlxGa1 − xN alloys along the c-axis and grading the magnitude of the intrinsic polarization in the wurtzite crystal structure. These free charges become the free electrons and holes which make up a device structure

Methods

Results

Conclusion