Heteroepitaxial undoped ZnO films were grown on Si(100) substrates by radio-frequency reactive sputtering, and then some of the samples were annealed at N2-800℃(Sample 1,S1) and O_2-800℃(Sample 2,S2) for 1h,respectively.The electrical transport characteristics of a ZnO/p-Si heterojunction were investigated.We found two interesting phenomena.First,the temperature coefficients of grain boundary resistances of S1 were positive(positive temperature coefficients,PTC) while that of both the as-grown sample and S2 were negative(negative temperature coefficients,NTC).Second,theⅠ-Ⅴproperties of S2 were similar to those common p-n junctions while that of both the as-grown sample and S1 had double Schottky barrier behaviors,which were in contradiction with the ideal p-n heterojunction model.Combined with the deep level transient spectra results,this revealed that the concentrations of intrinsic defects in ZnO grains and the densities of interfacial states in ZnO/p-Si heterojunction varied with the different annealing ambiences,which caused the grain boundary barriers in ZnO/p-Si heterojunction to vary.This resulted in adjustment electrical properties of ZnO/p-Si heterojunction that may be suitable in various applications.
ZnO films have been prepared on p-type Si substrates by metal-organic chemical vapour deposition (MOCVD) at different total gas flow rates. The current versus voltage and temperature (I-V-T ) characteristics, the deep-level transient spectroscopy (DLTS) and the photoluminescence (PL) spectra of the samples were measured. DLTS shows two deep-level centres of E1 (EC -0.13±0.02 eV) and E2 (EC -0.43±0.05 eV) in sample 1202a, which has a ZnO/p-Si heterostructure. A deep level at EC -0.13±0.01 eV was also obtained from the I-T characteristics. It was considered to be the same as E1 obtained from DLTS measurement. The emission related to this deep level center was detected by PL spectra. In addition, the energy location and the relative trap density of E1 was varied when the total gas flow rate was changed.
Heteroepitaxial undoped ZnO films were grown on Si(100) substrates by radio-frequency reactive sputtering, and then some of the samples were annealed at N2-800℃(Sample 1,S1) and O_2-800℃(Sample 2,S2) for 1h,respectively.The electrical transport characteristics of a ZnO/p-Si heterojunction were investigated.We found two interesting phenomena.First,the temperature coefficients of grain boundary resistances of S1 were positive(positive temperature coefficients,PTC) while that of both the as-grown sample and S2 were negative(negative temperature coefficients,NTC).Second,theⅠ-Ⅴproperties of S2 were similar to those common p-n junctions while that of both the as-grown sample and S1 had double Schottky barrier behaviors,which were in contradiction with the ideal p-n heterojunction model.Combined with the deep level transient spectra results,this revealed that the concentrations of intrinsic defects in ZnO grains and the densities of interfacial states in ZnO/p-Si heterojunction varied with the different annealing ambiences,which caused the grain boundary barriers in ZnO/p-Si heterojunction to vary.This resulted in adjustment electrical properties of ZnO/p-Si heterojunction that may be suitable in various applications.
