Low temperature p-type doping of (Al)GaN layers using ammonia molecular beam epitaxy for InGaN laser diodes
We demonstrate state-of-the-art p-type (Al) GaN layers deposited at low temperature (740 degrees C) by ammonia molecular beam epitaxy (NH3-MBE) to be used as top cladding of laser diodes (LDs) with the aim of further reducing the thermal budget on the InGaN quantum well active region. Typical p-type GaN resistivities and contact resistances are 0.4 Omega cm and 5 x 10(-4) Omega cm(2), respectively. As a test bed, we fabricated a hybrid laser structure emitting at 400 nm combining n-type AlGaN cladding and InGaN active region grown by metal-organic vapor phase epitaxy, with the p-doped waveguide and cladding layers grown by NH3-MBE. Single-mode ridge-waveguide LD exhibits a threshold voltage as low as 4.3V for an 800 x 2 mu m(2) ridge dimension and a threshold current density of similar to 5kAcm(-2) in continuous wave operation. The series resistance of the device is 6 Omega and the resistivity is 1.5 Omega cm, confirming thereby the excellent electrical properties of p-type Al0.06Ga0.94N:Mg despite the low growth temperature. (C) 2014 AIP Publishing LLC.