Determination of carrier diffusion length in GaN

作者：Hafiz Shopan^*; Zhang Fan; Monavarian Morteza; Avrutin Vitaliy; Morkoc Hadis; Oezguer Uemit; Metzner Sebastian; Bertram Frank; Christen Juergen; Gil Bernard

来源：Journal of Applied Physics, 2015, 117(1): 013106.

DOI：10.1063/1.4905506

Diffusion lengths of photo-excited carriers along the c-direction were determined from photoluminescence (PL) and cross-sectional cathodoluminescence (CL) measurements in p-and n-type GaN epitaxial layers grown on c-plane sapphire by metal-organic chemical vapor deposition. The investigated samples incorporate a 6 nm thick In0.15Ga0.85N active layer capped with either 500 nm p-GaN or 1500 nm n-GaN. The top GaN layers were etched in steps and PL from the InGaN active region and the underlying layers was monitored as a function of the top GaN thickness upon photo-generation near the surface region by above bandgap excitation. Taking into consideration the absorption in the top GaN layer as well as active and underlying layers, the diffusion lengths at 295K and at 15K were measured to be 93 +/- 7 nm and 70 +/- 7 nm for Mg-doped p-type GaN and 432 +/- 30 nm and 31 +/- 630 nm for unintentionally doped n-type GaN, respectively, at photogenerated carrier densities of 4.2 x 10(18) cm(-3) using PL spectroscopy. CL measurements of the unintentionally doped n-type GaN layer at much lower carrier densities of 10(17) cm(-3) revealed a longer diffusion length of 525 +/- 11nm at 6K.

• 出版日期2015-1-7