[18a-E310-1~10] 15.4 III-V-group nitride crystals

▲ [18a-E310-6] The influence of both Mg-concentration and excimer laser annealing (ELA) on p-AlGaN cladding layer for the application of AlGaN-based UVB Laser Diodes

〇(P)Muhammad Ajmal Khan¹, Juan Paolo Bermundo², Yasuaki Ishikawa², Hiroshi Ikenoue³, Sachie Fujikawa¹, Noritoshi Maeda¹, Masafumi Jo¹, Hideki Hirayama¹ (1.Riken Japan, 2.NAIST Japan, 3.Kyushu University Japan)

Keywords:Mg-doped p-AlGaN, UVB LEDs, UVB LDs

Mg-doped p-AlGaN is very attractive material for numerous applications in short wavelength light-emitting diodes, laser diodes and high power devices due to its outstanding properties such as large optical transmittance, possibility of doping using Mg-atoms, and having wide bandgap of p-AlGaN materials with direct bandgap (3.4~6.2eV). However, the activation of Mg-dopant in the p-AlGaN epitaxial layer is very challenging. Therefore, in this work the influence of both Mg-concentration and excimer laser annealing (ELA) on p-AlGaN cladding layer for the application of AlGaN-based UVB laser diodes was investigated. In this regard, several samples (V24 (Mg:50sccm), V25a (Mg:50sccm), V25b (Mg:70sccm), V25c (Mg:80sccm) and V26 (Mg:100sccm)) of Mg-doped p-AlGaN layers having thickness of 1.4µm were grown on the 4µm-thick AlN template on sapphire substrate in MOCVD by changing the Mg-concentration. The crystallinity of the grown samples was investigated by using the XRD reciprocal space mapping (RSM) along (-1 -1 4) reflections and XRD rocking curve (XRC) measurement both along (102) and (002) planes. XRC around 300 arcsec for (002) and 460 for (101) diffraction were maintained, which reflects the reasonable level of defects in all samples except sample V26 (heavily Mg-doped: 100 sccm). The influence of the Mg-concentration on the relaxation of the p-AlGaN layer were also confirmed, however the Al-composition were not influenced by the Mg-concertation variation in all samples. The ELA technique was employed to irradiate and anneal the Mg-doped p-AGaN layers on AlN template. The PL spectral intensities were reasonably enhanced in both sample V25c and V26 after ELA treatment. Broader Ga 2p peak after ELA treatment suggesting higher Ga-Ga (77.4%) and lower Ga-N (15.6%) bonding in the sample V25c, as confirmed by XPS spectra.