Thickness and Mg doping of graded AlGaN layers: Influence on contact layer's structural and electrical properties for DUV emitters

• Published in: Materials science in semiconductor processing 2024-08, Vol.178, p.108452, Article 108452
• Main Authors: Majchrzak, D., Tran, L.M., Babij, M., Serafińczuk, J., Olszewski, W., Kuna, R., Opołczyńska, K., Piejko, A., Michałowski, P.P., Kudrawiec, R., Hommel, D.
• Format: Article
• Language: English
• Subjects: Graded AlGaN alloys; MOVPE; Polarization doping; Ultraviolet optoelectronics
• ISSN: 1369-8001; 1873-4081
• DOI: 10.1016/j.mssp.2024.108452

One of the methods to improve p-doping properties in (Al)GaN-based materials is using a technique called polarization doping. In our study, two sets of p-AlGaN contact layers with different thicknesses of the graded layer were deposited by metalorganic vapor phase epitaxy. The grown samples were investigated by atomic force microscopy, secondary ion mass spectrometry, X-ray diffraction and Hall effect measurements to study the influence of the thickness of the graded Al0.6→0Ga0.4→1N:Mg layer on the structural and the electrical properties of the whole grown structure. Additionally, theoretical calculations for the contact structures with different thicknesses of the p-Al0.6→0Ga0.4→1N graded layer were performed. The obtained results show that the concentration of p-type carriers on the p-GaN/p-AlGaN gradient interface decreases with increasing thickness of the graded layer. Our findings reveal that among the graded structures the highest concentration of holes, 1.2 × 1018 cm−3, was obtained for a structure with 50-nm-thick graded layer, while maintaining low sample resistivity. In addition, it was also shown that non-doping of the graded layer allows to improve electrical properties. [Display omitted] •Graded p-AlGaN contact layers were grown by metalorganic vapor phase epitaxy.•Study of impact of graded layer thickness on structural and electrical properties.•Hole concentration on p-GaN/graded p-AlGaN drops with increasing gradient thickness.•50-nm-thick graded structure hold the highest hole concentration of 1.2 × 1018 cm−3.•Non-doping of the graded layer allows to improve electrical properties.