Characteristics of Mg-doped and In–Mg co-doped p-type GaN epitaxial layers grown by metal organic chemical vapour deposition

Abstract

Mg-doped and In-Mg co-doped p-type GaN epilayers were grown using the metal organic chemical vapour deposition technique. The effect of In co-doping on the physical properties of p-GaN layer was examined by high resolution x-ray diffraction (HRXRD), transmission electron microscopy (TEM), Hall effect, photoluminescence (PL) and persistent photoconductivity (PPC) at room temperature. An improved crystalline quality and a reduction in threading dislocation density are evidenced upon In doping in p-GaN from HRXRD and TEM images. Hole conductivity, mobility and carrier density also significantly improved by In co-doping. PL studies of the In-Mg co-doped sample revealed that the peak position is blue shifted to 3.2 eV from 2.95 eV of conventional p-GaN and the PL intensity is increased by about 25%. In addition, In co-doping significantly reduced the PPC effect in p-type GaN layers. The improved electrical and optical properties are believed to be associated with the active participation of isolated Mg impurities.

Enhanced Mg Doping Efficiency in P-Type GaN by Indium-Surfactant-Assisted Delta Doping Method

“…The enhanced dopant solubility by using In surfactant was also confirmed by the other research groups. 9,10) It has been found that when In is fed into the reactor, the incorporation efficiency of Ga atoms is decreased sharply, bringing a higher effective V/III ratio at the growing surface and therefore a decrease of nitrogen vacancy (V N ) in the epilayer. 10) Moreover, the decreased Ga incorporation can provide III-group vacancies to be occupied by Mg atoms, improving the incorporation efficiency of Mg atoms.…”

Analysis of Photoluminescence Thermal Quenching: Guidance for the Design of Highly Effective p-type Doping of Nitrides

“…In this work, extremely high V/III ratios (10000:1) and high growth temperatures (1050 °C) are used to yield sufficient amounts of active nitrogen species for gallium nitride growth, which is helpful for ammonias cracking and transport of atomic N to proper lattice sites. The strain analyses by XRD published by our group previously have confirmed the elimination of nitrogen vacancies in Indium doped nitrides by using non-equilibrium growth techniques24, which is consist with the results of Chung25. To get more effective p doping for nitrides, better approaches to suppress N vacancy are still highly desired.…”

Analysis on the enhanced hole concentration in p‐type GaN grown by indium‐surfactant‐assisted Mg delta doping

“…The Mg concentration increased from 8.8 × 10 18 cm −3 to 1.2 × 10 19 cm −3 when using indium‐surfactant‐assisted δ‐doping, which plays a key role in the enhancement of hole concentration. It has been proposed that when In is fed into the reactor, the incorporation efficiency of Ga atoms may be decreased sharply, resulting in the higher effective V/III ratio in the growth interface and the subsequent suppression of V N . In addition, since the binding energy of the InN bond (1.98 eV) is lower than that of the GaN bond (2.20 eV) , In atoms are preferentially desorbed from the surface during the purge step of δ‐doping as compared with the Ga atoms .…”