Polarization-Induced Hole Doping in Wide–Band-Gap Uniaxial Semiconductor Heterostructures

TLDR

Semiconductor LEDs and lasers require wide bandgap materials for short wavelengths, but their conductivity must be enhanced by doping, and in nitride semiconductors such as GaN and AlGaN, Mg acceptor doping fails at room temperature. A graded AlGaN/GaN heterostructure was grown, showing that polarization‑induced field ionization of acceptor dopants enables efficient hole doping at room temperature, and the structure powered a UV‑emitting LED. Simon et al.

Abstract

Activating Stubborn Dopants Many applications of semiconductor light-emitting diodes and lasers, such as reading optical disks, benefit from shorter wavelengths, but this requires materials with larger energy gaps between their valance and conduction bands. The electronic conductivity of these materials often has to be increased by doping with impurity atoms. However, in nitride materials, such as GaN and AlGaN, hole doping with acceptor atoms such as Mg is ineffective at room temperature. Simon et al. (p. 60 ) grew a gradient of AlGaN on the surface of GaN and found that the polarization of the layer could field-ionize the acceptor dopants efficiently at room temperature. The heterostructure was used successfully in a light-emitting diode that emits in the ultraviolet.