Effects of AIInN graded polarization-dependent doped top cladding on the performance of deep ultra-violet laser diode emitting at ～271 nm wavelength

摘要

This work presents the theoretical study on the polarization induced p-type doping of undoped-AlInN graded cladding layers for the deep ultra-violet laser diode (LD) emitting at around 271 nm wavelength. The reference LD consists of 320 nm of linearly graded undoped AlN-Al0.7Ga0.3N layer, while in our LD the graded undoped AlN-Al0.7Ga0.3N layer is replaced by the undoped AlN-AlxIn(1-x)N composition graded layers with different x mole fraction from 0.88 to 0.92. The static device resistance for reference LD is similar to 28.6 omega which is reduced to similar to 18.38 omega for AlN-Al0.12In0.88N graded layer at 500 mA. The device resistance has been reduced dramatically by similar to 10.2 omega. The reduction in resistance is attributed to the increased polarization grading in AlN-Al0.12In0.88N. The large polarization grading leads to large hole carrier induction in the layer which increases the p-type conductivity of the undoped AlN-Al0.12In0.88N graded layer. Threshold current for reference LD is 393 mA which has been reduced to 384 mA for AlN-Al0.12In0.88N. The electron leakage has reduced from 0.9 kA cm(-2) to 0.11 kA cm(-2) at similar to 30 kA cm(-2) injected current density, whereas the hole transportation has improved from 29.23 kA cm(-2) to similar to 30 kA cm(-2) at similar to 30 kA cm(-2) injected current density.