The electron transport behavior across the interface plays an important role in determining the performance of op- toelectronic devices based on heterojunctions. Here through growing CdS thin film on silicon nanoporou...The electron transport behavior across the interface plays an important role in determining the performance of op- toelectronic devices based on heterojunctions. Here through growing CdS thin film on silicon nanoporous pillar array, an untraditional, nonplanar, and multi-interface CdS/Si nanoheterojunction is prepared. The current density versus voltage curve is measured and an obvious rectification effect is observed. Based on the fitting results and model analyses on the forward and reverse conduction characteristics, the electron transport mechanism under low forward bias, high forward bias, and reverse bias are attributed to the Ohmic regime, space-charge-limited current regime, and modified Poole-Frenkel regime respectively. The forward and reverse electrical behaviors are found to be highly related to the distribution of inter- facial trap states and the existence of localized electric field respectively. These results might be helpful for optimizing the preparing procedures to realize high-performance silicon-based CdS optoelectronic devices.展开更多
Polycrystalline thick film of zinc oxide （ZnO） is grown on a unique silicon substrate with a hierarchical structure, silicon nanoporous pillar array （Si-NPA）, by using a vapour phase transport method. It is found ...Polycrystalline thick film of zinc oxide （ZnO） is grown on a unique silicon substrate with a hierarchical structure, silicon nanoporous pillar array （Si-NPA）, by using a vapour phase transport method. It is found that as-grown ZnO film is composed of closely packed ZnO crystallites with an average size of -10 μm. The film resistivity of ZnO/SiNPA is measured to be -8.9Ωcm by the standard four probe method. The lengthwise Ⅰ-Ⅴ curve of ZnO/Si-NPA heterostructure is measured. Theoretical analysis shows that the carrier transport across ZnO/Si-NPA heterojunction is dominated by two mechanisms, i.e. a thermionic process at high voltages and a quantum tunnelling process at low voltages.展开更多
A GaN/Si nanoheterojunction is prepared through growing Ga N nanocrystallites（nc-GaN） on a silicon nanoporous pillar array（Si-NPA） by a chemical vapor deposition（CVD） technique at a relatively low temperature. T...A GaN/Si nanoheterojunction is prepared through growing Ga N nanocrystallites（nc-GaN） on a silicon nanoporous pillar array（Si-NPA） by a chemical vapor deposition（CVD） technique at a relatively low temperature. The average size of nc-Ga N is determined to be ~10 nm. The spectral measurements disclose that the photoluminescence（PL） from GaN/SiNPA is composed of an ultraviolet（UV） band and a broad band spanned from UV to red region, with the feature that the latter band is similar to that of electroluminescence（EL）. The electron transition from the energy levels of conduction band and, or, shallow donors to that of deep acceptors of Ga N is indicated to be responsible for both the broad-band PL and the EL luminescence. A study of the I-V characteristic shows that at a low forward bias, the current across the heterojunction is contact-limited while at a high forward bias it is bulk-limited, which follows the thermionic emission model and space-charge-limited current（SCLC） model, respectively. The bandgap offset analysis indicates that the carrier transport is dominated by electron injection from n-GaN into the p-Si-NPA, and the EL starts to appear only when holes begin to be injected from Si-NPA into GaN with biases higher than a threshold voltage.展开更多
基金Project supported by the National Natural Science Foundation of China(Grant Nos.61176044 and 11074224)the Science and Technology Project for Innovative Scientist of Henan Province,China(Grant No.1142002510017)the Science and Technology Project on Key Problems of Henan Province,China(Grant No.082101510007)
文摘The electron transport behavior across the interface plays an important role in determining the performance of op- toelectronic devices based on heterojunctions. Here through growing CdS thin film on silicon nanoporous pillar array, an untraditional, nonplanar, and multi-interface CdS/Si nanoheterojunction is prepared. The current density versus voltage curve is measured and an obvious rectification effect is observed. Based on the fitting results and model analyses on the forward and reverse conduction characteristics, the electron transport mechanism under low forward bias, high forward bias, and reverse bias are attributed to the Ohmic regime, space-charge-limited current regime, and modified Poole-Frenkel regime respectively. The forward and reverse electrical behaviors are found to be highly related to the distribution of inter- facial trap states and the existence of localized electric field respectively. These results might be helpful for optimizing the preparing procedures to realize high-performance silicon-based CdS optoelectronic devices.
基金Project supported by the National Natural Science Foundation of China （Grant No 10574112）.
文摘Polycrystalline thick film of zinc oxide （ZnO） is grown on a unique silicon substrate with a hierarchical structure, silicon nanoporous pillar array （Si-NPA）, by using a vapour phase transport method. It is found that as-grown ZnO film is composed of closely packed ZnO crystallites with an average size of -10 μm. The film resistivity of ZnO/SiNPA is measured to be -8.9Ωcm by the standard four probe method. The lengthwise Ⅰ-Ⅴ curve of ZnO/Si-NPA heterostructure is measured. Theoretical analysis shows that the carrier transport across ZnO/Si-NPA heterojunction is dominated by two mechanisms, i.e. a thermionic process at high voltages and a quantum tunnelling process at low voltages.
基金Project supported by the National Natural Science Foundation of China(Grant No.61176044)
文摘A GaN/Si nanoheterojunction is prepared through growing Ga N nanocrystallites（nc-GaN） on a silicon nanoporous pillar array（Si-NPA） by a chemical vapor deposition（CVD） technique at a relatively low temperature. The average size of nc-Ga N is determined to be ~10 nm. The spectral measurements disclose that the photoluminescence（PL） from GaN/SiNPA is composed of an ultraviolet（UV） band and a broad band spanned from UV to red region, with the feature that the latter band is similar to that of electroluminescence（EL）. The electron transition from the energy levels of conduction band and, or, shallow donors to that of deep acceptors of Ga N is indicated to be responsible for both the broad-band PL and the EL luminescence. A study of the I-V characteristic shows that at a low forward bias, the current across the heterojunction is contact-limited while at a high forward bias it is bulk-limited, which follows the thermionic emission model and space-charge-limited current（SCLC） model, respectively. The bandgap offset analysis indicates that the carrier transport is dominated by electron injection from n-GaN into the p-Si-NPA, and the EL starts to appear only when holes begin to be injected from Si-NPA into GaN with biases higher than a threshold voltage.
