Effect of doping on the intersubband absorption in Si- and Ge-doped GaN/AlN heterostructures

TL;DR

This study investigates how Si and Ge doping affect intersubband absorption in GaN/AlN heterostructures, revealing comparable performance in planar and nanowire forms and analyzing doping-induced spectral shifts.

Contribution

It provides a comparative analysis of Si and Ge doping effects on intersubband absorption in GaN/AlN heterostructures, including nanowire configurations, and examines many-body effects on spectral shifts.

Findings

Nanowire heterostructures show longer photoluminescence decay times.

Ge-doped quantum wells achieve intersubband absorption at 1.45-1.75 microns.

Dopant choice (Si vs. Ge) does not significantly impact intersubband phenomena.

Abstract

In this paper, we study band-to-band and intersubband characteristics of GaN/AlN heterostructures (planar and nanowires) structurally designed to absorb in the short-wavelength infrared region, particularly at 1.55 microns. We compare the effect of doping the GaN sections with Si and Ge, and we discuss the variation of free-carrier screening with the doping density and well/nanodisk size. We observe that nanowire heterostructures consistently present longer photoluminescence decay times than their planar counterparts, which supports the existence of an in-plane piezoelectric field associated to the shear component of the strain tensor, leading to lateral electron-hole separation. We report intersubband absorption covering 1.45 microns to 1.75 microns using Ge-doped quantum wells, with comparable performance to well-studied Si-doped planar heterostructures. We also report comparable intersubband absorption in Si- and Ge-doped nanowire heterostructures indicating that the choice of dopant is not an intrinsic barrier for observing intersubband phenomena. In addition, we calculate the spectral shift of the intersubband absorption due to many body effects as a function of the doping concentration.