Shubnikov-de Haas oscillations in coherently strained AlN/GaN/AlN quantum wells on bulk AlN substrates

TL;DR

This study demonstrates the observation of Shubnikov-de Haas oscillations in coherently strained AlN/GaN/AlN quantum wells, enabling direct measurement of key 2DEG parameters crucial for high-performance nitride electronic devices.

Contribution

The paper presents the first direct measurement of 2DEG parameters in coherently strained AlN/GaN/AlN quantum wells using SdH oscillations, including carrier density, effective mass, and quantum scattering time.

Findings

Single and two subband occupation in undoped and δ-doped QWs.

Quantitative values of effective mass and quantum scattering time.

Insights into fundamental 2DEG properties in strained GaN QWs.

Abstract

We report the observation of Shubnikov-de Haas (SdH) oscillations in coherently strained, low-dislocation AlN/GaN/AlN quantum wells (QWs), including both undoped and $\delta$-doped structures. SdH measurements reveal a single subband occupation in the undoped GaN QW and two subband occupation in the $\delta$-doped GaN QW. More importantly, SdH oscillations enable direct measurement of critical two-dimensional electron gas (2DEG) parameters at the Fermi level: carrier density and ground state energy level, electron effective mass ($m^* \approx 0.289\,m_{\rm e}$ for undoped GaN QW and $m^* \approx 0.298\,m_{\rm e}$ for $\delta$-doped GaN QW), and quantum scattering time ($\tau_{\rm q} \approx 83.4 \, \text{fs}$ for undoped GaN QW and $\tau_{\rm q} \approx 130.6 \, \text{fs}$ for $\delta$-doped GaN QW). These findings provide important insights into the fundamental properties of 2DEGs that are strongly quantum confined in the thin GaN QWs, essential for designing nitride heterostructures for high-performance electronic applications.