Current transport through an n-doped, nearly lattice matched GaN/AlInN/GaN heterostructure

The low refractive index of AlInN makes it a strong candidate as a waveguide cladding layer for lasers emitting from the blue to the green. A sequence of AlInN layers interfaced periodically with GaN is needed to provide a smooth surface for growth of quantum wells. The current transport across a highly doped single 54 nm thick layer of AlInN clad by GaN is analysed and is shown to be dominated by the heterointerfaces. Greater than 1 V is required to obtain current densities required in lasers of several kA/cm ². Frequency dependent electrical reflection measurements show that a 20 nm wide depletion zone is present at the interfaces even under bias and despite the high doping levels. A thermally activated resistive shunting of the interface is relevant at low voltages while the current is dominated by tunnelling at laser current densities. A low defect density AlInN/GaN multilayer structure requires > 10 V in order to drive current at levels needed in a laser diode.