InGaN laser diode with metal-free laser ridge using n⁺-GaN contact layers

Abstract

We report on InGaN edge emitting laser diodes with a top metal electrode located beside the laser ridge. Current spreading over the ridge is achieved via a highly doped n+-type GaN layer deposited on top of the structure. The low sheet resistance of the n+-GaN layer ensures excellent lateral current spreading, while carrier injection is confined all along the ridge thanks to current tunneling at the interface between the n+-GaN top layer and the p++-GaN layer. Continuous-wave lasing at 400 nm with an output power of 100 mW is demonstrated on uncoated facet devices with a threshold current density of 2.4 kA·cm−2.

Tunnel-injected sub 290 nm ultra-violet light emitting diodes with 2.8% external quantum efficiency

“…Low resistance (<1 mX cm 2 ) GaN tunnel junctions have been achieved by polarization engineering [19][20][21] or degenerate doping. [22][23][24][25] The incorporation of GaN tunnel junctions has led to successful demonstrations of blue LEDs 10,24-26 with a wall-plug efficiency higher than 70%, 14 cascaded LEDs, 11,27,28 edge emitting laser diodes, 29,30 and vertical-cavity surface-emitting laser diodes. 23 However, the fabrication of low resistance and low voltage consumption tunnel junctions for ultra-wide bandgap AlGaN is challenging because of the wide depletion barrier and doping limitations.…”

True-blue laser diodes with tunnel junctions grown monolithically by plasma-assisted molecular beam epitaxy

“…In such design, air (with refractive index equal to 1) acts as a cladding and helps to confine the optical mode inside the waveguide, and the top AlGaN cladding thickness can be substantially reduced. 10) Despite the high application potential and extensive efforts in incorporating TJs into the nitride device structure, there are no such devices available in the market. This is due to fundamental challenges with the activation of p-type conductivity in buried Mg-doped layers in devices grown by the commonly used metalorganic vapor phase epitaxy (MOVPE).…”

“…Promising results for new types of edge-emitting LD or VCSEL have been reported recently for hybrid MOVPE=MBE growth in which the active part of the device was grown by MOVPE and the p-n TJ was made by MBE. [8][9][10]20) The p-n tunnel junction was demonstrated for narrowbandgap materials in 1958. 21) The theory of the p-n TJ indicates that the transmission probability of carriers through such a junction depends on the depletion width.…”

“…In addition, the application of TJs will be extremely important for (a) UV LDs and LEDs, in which the challenges for p-type conductivity are more serious than those for visible optoelectronics owing to the larger Mg activation energy and (b) monolithic verticalcavity surface-emitting lasers (VCSELs) or edge-emitting LDs where new designs of device architectures are needed. 3,5,9,10) The edge-emitting LDs with TJs have more freedom in the design of the upper cladding and top metal contact. For example, owing to the high conductivity of n-type layers on top of the TJ, the metal contact can be deposited outside the laser mesa.…”

“…[2][3][4][5][6][7][8][9][10] Efficient TJs may find very important applications in injecting holes into the p-type region of LDs and LEDs, and thus TJs can open new possibilities in the design and architecture of III-nitride devices. The implementation of TJs to interconnect LD structures grown on top of one another paves the way to high-power nitride devices.…”