Compact, solid‐state UV emitters have many potential applications, and ZnO‐based materials are ideal for the wavelength range 390 nm and lower. However, the most efficient solid‐state emitters are p–n junctions, and p‐type ZnO is difficult to make. Thus, the future of ZnO light emitters depends on either producing low‐resistivity p‐type ZnO, or in mating n‐type ZnO with a p‐type hole injector. Perhaps the best device so far involves an n‐ZnO/p‐AlGaN/n‐SiC structure, which produces intense 390 ± 1 nm emission at both 300 K and 500 K. However, development of p‐ZnO is proceeding at a rapid pace, and a p–n homojunction should be available soon. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

A UV‐light‐emitting homojunction ZnO LED is grown by radiofrequency sputtering at high temperature, improving the structural, electrical, and optical properties of the n‐ and p‐type ZnO layers. The figure shows a comparison of the electroluminescence spectra of A) a p–n homojunction ZnO LED and B) a ZnO LED with Mg0.1Zn0.9O layers used as energy barrier layers. Such materials are of interest for their potential use in long‐lifetime solid‐state lighting, high‐density information storage, secure communication, and chemical/biological‐agent monitoring.

Amorphous silicon quantum dots (a-Si QDs), which show a quantum confinement effect were grown in a silicon nitride film by plasma-enhanced chemical vapor deposition. Red, green, blue, and white photoluminescence were observed from the a-Si QD structures by controlling the dot size. An orange light-emitting diode (LED) was fabricated using a-Si QDs with a mean size of 2.0 nm. The turn-on voltage was less than 5 V. An external quantum efficiency of 2×10−3% was also demonstrated. These results show that a LED using a-Si QDs embedded in the silicon nitride film is superior in terms of electrical and optical properties to other Si-based LEDs.

Disorder induced semiconductor to metal transition and modifications of grain boundaries in nanocrystalline zinc oxide thin film J. Appl. Phys. 112, 073101 (2012) Robust low resistivity p-type ZnO:Na films after ultraviolet illumination: The elimination of grain boundaries Appl. Phys. Lett. 101, 122109 (2012) P-type ZnO thin films achieved by N+ ion implantation through dynamic annealing process Appl. Phys. Lett. 101, 112101 (2012) Controlling the resistivity gradient in aluminum-doped zinc oxide grown by plasma-enhanced chemical vapor deposition J. Appl. Phys. 112, 043708 (2012) Schottky solar cells based on CsSnI3 thin-films Appl.

Surface-architecture-controlled ZnO nanowires were grown using a vapor transport method on various ZnO buffer film coated c-plane sapphire substrates with or without Au catalysts. The ZnO nanowires that were grown showed two different types of geometric properties: corrugated ZnO nanowires having a relatively smaller diameter and a strong deep-level emission photoluminescence (PL) peak and smooth ZnO nanowires having a relatively larger diameter and a weak deep-level emission PL peak. The surface morphology and size-dependent tunable electronic transport properties of the ZnO nanowires were characterized using a nanowire field effect transistor (FET) device structure. The FETs made from smooth ZnO nanowires with a larger diameter exhibited negative threshold voltages, indicating n-channel depletion-mode behavior, whereas those made from corrugated ZnO nanowires with a smaller diameter had positive threshold voltages, indicating n-channel enhancement-mode behavior.