Nanoscale analysis of MOCVD-grown Mg-doped AlxGa_1−xN/GaN quantum well infrared photodetector (QWIP): Insights into dopant distribution and device performance

Quantum well infrared photodetectors (QWIPs) have emerged as a high-performance and versatile platform for IR detection applications owing to their design flexibility, fast response time, and wavelength tunability across a wide spectral range. While research and development in this field have predominantly focused on GaAs-based QWIPs owing to their mature growth technique and well-understood material properties, III-nitride-based QWIPs can offer potential advantages such as a wider bandgap and strong polarization charges. However, the study of GaN-based QWIPs is still in its early stages and requires further exploration to achieve optimal device performance. Compared to n-QWIPs, p-QWIPs allow for normal-incident absorption, significantly reducing device complexity and size by eliminating the light coupler, which is particularly advantageous for hand-held and imaging applications. We perform detailed atomic-scale characterization of the distribution of Mg acceptors in layers and at interfaces of a Mg-doped AlGaN/GaN p-QWIP grown by metal organic chemical vapor deposition. Device design, device structure growth conditions, and electrical characterization of the QWIP are presented. Initial electrical characterizations revealed a small but noticeable increase in photocurrent upon illumination. We suspect that photoresponsivity (∼μA/W) is highly impacted by low or inefficient Mg incorporation in the QWIP, limiting the carrier population in quantum wells. Atom probe tomography was employed to study the Mg concentration and distribution in the Mg-doped AlGaN/GaN p-QWIP and revealed Mg segregation and clustering in QWIP layers. These findings provide critical insights and pathways to enhance photoresponsivity and overall device performance in QW-based devices that require Mg p-doping.