Optoelectronic Devices with III-Nitride Nanostructures and Monolayer Heterostructures

Abstract:

The III-Nitrides have emerged as a leading material group for a wide range of optoelectronic applications including but not limited to commercial solid-state lighting, plastic fiber communication, light detection, RF and high-power switching, deep-UV photonics, single photon sources for quantum computing and cryptography, and the study of exciton dynamics. The versatility of these materials allows them to be epitaxially-grown in bulk (3D), planar (2D), nanowire (1D), or quantum dot (0D) form by careful control of the growth conditions. The composition of the Al(Ga)N and In(Ga)N ternaries allows complete coverage of the deep-UV to IR spectrum. These materials can be grown on a wide range of substrates including free-standing GaN, sapphire, SiC, and silicon. Silicon is most economical and of interest for monolithic integration. However the large lattice mismatch ~17% with GaN requires careful strain engineering to prevent propagation of threading dislocations, which are detrimental to device operation.

In the present study, Al_0.56Ga_0.44N/Al_0.62Ga_0.38N multi-quantum well heterostructures for deep-UV emitters will be optically and structurally characterized. A high-gain photodetector using InGaN/GaN disk-in-nanowires is demonstrated. High exciton binding energies ~200 meV are measured in GaN monolayers. The monolayers are characterized and a photodiode is presented in collaboration. An LED using InGaN/GaN quantum dots (QDs) grown on coalesced GaN/silicon is characterized. Pump-probe spectroscopy of the QDs is presented in collaboration with IIT Bombay.

Chair: Professor Pallab Bhattacharya

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