In principle, InGaN has a unique ability to span the entire solar spectral range creating a highly efficient mechanism for photovoltaic conversion. However, in practice several present technology limitations exist including but not limited to defects resultant from lattice mismatch and p-type doping limitations which would lower the usable spectral range to far less than often promoted by InGaN supporters. Herein, we will present the reasons for looking at InGaN for photovoltaics, show its limitations based on today’s materials technology and present the state of the art in InGaN photovoltaic performance.

Multifunctional materials, materials that interact with their environment via differing force mechanisms, including but not limited to electrostatic, magnetic, acoustic, photonic, and chemical, are of great interest for future advanced applications. Lithium metal oxide multifunctional materials, including LiNbO2, LiNbO3, LiTaO2 and LiTaO3 are presented as a promising but challenging materials for multifunctional devices. Example proposed applications will be presented. A chloride based chemistry that bypasses many of the traditional pitfalls of Lithium Niobate (LN) has been developed. The present state of homoepitaxy and heteroepitaxy of LN on semiconductors is presented. It is shown that control of oxygen stiochiometry through vacuum conditions allows the new semiconductor, LiNbO2 to be preferentially grown over LiNbO3 in the oxygen deficient MBE vacuum environment. While the demonstrated metal chloride based epitaxy is shown as a viable candidate for MBE of multifunctional refractory metal oxides, particularly for electronic applications, the possibility for thicker films, and thus impact on optical devices, is currently limited by the available Li source. Efforts to circumvent this difficulty, including a large volume valved Li source, will be described.

While having a diverse topical coverage, the hope is to convey a useful approach to electronic/optoelectronic design driven by the questions: 1) What new device can you envision? 2) What new materials/device structures will make this device a reality? and finally, 3) What tooling/techniques are needed to achieve these materials? It will be shown that the ordering of these questions largely dictates whether the research is engineering based or science based and whether or not it will result in a useful device.