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A comprehensiveinvestigation was carried out on n-type ZnO nanowiresfor studying the temperature dependence of the piezotronic effectfrom 77 to 300 K. In general, lowering the temperature results ina largely enhanced piezotronic effect. The experimental results showthat the behaviors can be divided into three groups depending on thecarrier doping level or conductivity of the ZnO nanowires. For nanowireswith a low carrier density (<1017/cm3at77 K), the pieozotronic effect is dominant at low temperature fordictating the transport properties of the nanowires; an opposite changeof Schottky barrier heights at the two contacts as a function of temperatureat a fixed strain was observed for the first time. At a moderate doping(between 1017/cm3and 1018/cm3at 77 K), the piezotronic effect is only dominant at onecontact, because the screening effect of the carriers to the positivepiezoelectric polarization charges at the other end (for n-type semiconductors).For nanowires with a high density of carriers (>1018/cm3at 77 K), the piezotronic effect almost vanishes.This studynot only proves the proposed fundamental mechanism of piezotroniceffect, but also provides guidance for fabricating piezotronic devices. [ABSTRACT FROM AUTHOR]

We present that the electroluminescence (EL) propertiesof Mg-doped p-type GaN thin films can be tuned bythe piezo-phototroniceffect via adjusting the minority carrier injection efficiency atthe metal–semiconductor (M–S) interface by strain inducedpolarization charges. The device is a metal–semiconductor–metalstructure of indium tin oxide (ITO)–GaN–ITO. Under differentstraining conditions, the changing trend of the transport propertiesof GaN films can be divided into two types, corresponding to the different c-axis orientations of the films. An extreme value was observedfor the integral EL intensity under certain applied strain due tothe adjusted minority carrier injection efficiency by piezoelectriccharges introduced at the M–S interface. The external quantumefficiency of the blue EL at 430 nm was changed by 5.84% under differentstraining conditions, which is 1 order of magnitude larger than thechange of the green peak at 540 nm. The results indicate that thepiezo-phototronic effect has a larger impact on the shallow acceptorstates related EL process than on the one related to the deep acceptorstates in p-type GaN films. This study has greatsignificance on the practical applications of GaN in optoelectronicdevices under a working environment where mechanical deformation isunavoidable such as for flexible/printable light emitting diodes. [ABSTRACT FROM AUTHOR]