Heterostructure light-emitting diodes(LEDs)were fabricated by growing ZnO nanorods and undoped ZnO films on p-GaN templates.The heterojunction showed a diode-like I–V characteristic and emitted electroluminescence(EL)peaks at 383 nm,402 nm,438 nm,and 507 nm under forward bias.Since the electrons from ZnO nanorods and the holes from p-GaN could be injected into ZnO films with a relatively low carrier concentration and mobility,the radiative recombination was mainly confined in the ZnO film region.As a result,the ZnO nanorods/i-ZnO/p-GaN light emitting diode exhibits a stronger ultraviolet–violet emission peak.
n-ZnO/p-GaN heterojunction light-emitting diodes with and without a Ga2O3 interlayer are fabricated. The electroluminescence(EL) spectrum of the n-ZnO/p-GaN displays a single blue emission at 430 nm originating from GaN, while the n-ZnO/Ga2O3/p-GaN exhibits a broad emission peak from ultraviolet to visible. The broadened EL spectra of n-ZnO/Ga2O3/p-GaN are probably ascribed to the radiative recombination in both the p-GaN and n-ZnO, due to the larger electron barrier( EC= 1.85 eV) at n-ZnO/Ga2O3 interface and the much smaller hole barrier( EV= 0.20 eV) at Ga2O3/p-GaN interface.
ZnO/diamond-like carbon(DLC)thin films are deposited by pulsed laser deposition(PLD),and the room-temperature photoluminescence(PL)is investigated.Using a fluorescence spectrophotometer,we obtain the PL spectra of DLC/Si and ZnO/Si thin films deposited at different substrate temperatures.The ZnO/DLC thin films show a broadband emission almost containing the entire visible spectrum.The Gaussian fitting curves of PL spectra reveal that the visible emission of ZnO/DLC thin films consists of three peaks centered at 381 nm,526 nm and 682 nm,which are attributed to the radiative recombination of ZnO and DLC,respectively.The Commission International de l,Eclairage(CIE)1931(x,y)chromaticity space of ZnO/DLC thin films indicates that the visible PL spectrum is very close to the standard white-light region.
Optoelectronic characteristics of p-type CuO nanorods, synthesized by a simple hydrothermal method, were investigated at different atmospheres and oxygen pressures. The CuO nanorods have lower resistance in air than in a vacuum, unlike the n-type semiconductors. This is explained in terms of the surface accumulation conduction. Measurements at different oxygen pressures indicate that oxygen has an important effect on the optoelectronic properties of p-type nanomaterials.
