Interfacial passivation of n-ZnO/p-Si heterojunction by CuI thin layer

The ZnO/Si heterojunction diode can be integrated with the Si process, which has attracted great attention in recent years. However, the large number of interface states at the ZnO/Si heterojunction interface could adversely affect its optoelectronic properties. Here, n-type ZnO thin film was deposited on p-Si substrate for formation of an n-ZnO/p-Si heterojunction substrate. To passivate the ZnO/Si interface, a thin Cul film interface passivation layer was inserted at the ZnO/p-Si heterojunction interface. Electrical characterization such as I-V and C-V characteristic curves confirmed the significant improvement of the heterojunction properties e.g. enhancement of forward current injection, reduction of reverse current and improvement of the rectification ratio. These results showed that the passivation of interface is critical for ZnO/Si heterojunctions.

Heteroepitaxial Growth and Heterojunction Characteristics of Voids-Free n-3C-SiC on p-Si(100)

Highly oriented voids-free 3C-SiC heteroepitaxial layers are grown onφ50mm Si (100) substrates by low pressure chemical vapor deposition (LPCVD).The initial stage of carbonization and the surface morphology of carbonization layers of Si (100) are studied using reflection high energy electron diffraction (RHEED) and scanning electron microscopy (SEM).It is shown that the optimized carbonization temperature for the growth of voids-free 3C-SiC on Si (100) substrates is 1100℃.The electrical properties of SiC layers are characterized using Van der Pauw method.The I-V,C-V,and the temperature dependence of I-V characteristics in n-3C-SiC/p-Si heterojunctions with AuGeNi and Al electrical pads are investigated.It is shown that the maximum reverse breakdown voltage of the n-3C-SiC/p-Si heterojunction diodes reaches to 220V at room temperature.These results indicate that the SiC/Si heterojunction diode can be used to fabricate the wide bandgap emitter SiC/Si heterojunction bipolar transistors (HBT's).

Temperature coefficients of grain boundary resistance variations in a ZnO/p-Si heterojunction

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 02-800℃ （Sample 2, S2） for 1 h, 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 S 1 were positive （positive temperature coefficients, PTC） while that of both the as-grown sample and S2 were negative （negative temperature coefficients, NTC）. Second, the I-V properties of S2 were similar to those common p-n junctions while that of both the as-grown sample and S 1 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 ofZnO/p-Si heterojunction that may be suitable in various applications.

Photoelectric characteristics of CH_3NH_3PbI_3/p-Si heterojunction

Organic-inorganic hybrid perovskite CH3NH3PbI3 film is prepared on p-type silicon substrate using the one-step solution method to form a CHaNH3PbI3/p-Si heterojunction. The film morphology and structure are characterized by atomic force microscopy （AFM） and scanning electron microscopy （SEM）. The photoelectric properties of the CHaNHaPbIa/p-Si heterojunction are studied by testing the current-voltage （I-V） with and with- out illumination and capacitance-voltage （C-V） characteristics. It turns out from the I-V curve without illumina- tion that the CH3NH3PbI3/p-Si heterojunction has a rectifier feature with the rectification ratio over 70 at the bias of 4-5 V. Also, there appears a photoelectric conversion phenomenon on this heterojunction with a short circuit current （I sc） of 0.16 #A and an open circuit voltage （Voc） of about 10 mV. The high frequency C-V characteristic of the Ag/CH3NH3PbI3/p-Si heterojunction turns out to be similar to that of the metal-insulator-semiconductor （MIS） structure, and a parallel translation of the C-V curve along the forward voltage axis is found. This paral- lel translation means the existence of defects at the CH3NH3PbI3/p-Si interface and positive fixed charges in the CH3NH3PbI3 layer. The defects at the interface of the CH3NH3PbI3/p-Si heterojunction result in the dramatic decline of the Voc. Besides, the C-V test of CH3NH3Pbl3 film shows a non-linear dielectric property and the dielectric value is about 4.64 as calculated.

n-ZnO/p-Si紫外至近红外增强型广谱光探测器

采用直流反应溅射法，在一定的溅射功率和衬底温度等条件下控制气体组分，优选Ar：O2—8：1成功研制出高响应度n-ZnO／p-Si紫外至近红外增强型广谱光探测器。实验关键是利用缺O法在n-ZnO薄膜内有效引入O缺位Vo，而Vo可增强紫蓝波段的光响应。测试结果显示，ZnO薄膜的光致发光（PL）谱除在388nm处存在紫外带边发射主峰外，还在416nm处出现由O缺位导致的发射峰；X射线衍射（XRD）谱表明，薄膜中的晶体为高C轴取向的纤锌矿结构；n-ZnO／p-Si光探测器在光照时Ⅰ-Ⅴ特性显示，光电流随反向偏压的增加迅速上升；在5V的反向偏压下，紫外区（310-388nm）的光响应高达0．75～1．38A／W，紫蓝光区（400-430nm）的光响应大大增强，400-800nm波段的光谱响应稳定在0．90A／W。

LP-MOCVD法制作n-ZnO/p-Si异质结及其电致发光研究

采用低压-金属有机化学气相沉积法(LP-MOCVD)在(100)p-Si衬底上制备未掺杂n型ZnO薄膜,并制作了相应的n-ZnO/p-Si异质结器件。通过X射线衍射(XRD)、光致发光(PL)光谱和霍尔测试分别研究了所制备薄膜的结构、光学和电学特性,得到具有较高质量的n型ZnO薄膜。在室温条件下,测得了该类异质结器件正向注入电流下可见光和近红外区域的电致发光(EL)。

Luminescence and recombine centre in ZnO/Si films

The D0h luminescence of ZnO films deposited on p-type Si substrates is produced by metal-organic chemical vapor deposition(MOCVD).After annealing in the air at 700°C for an hour,the photoluminescence(PL)spectra,the I-V characteristics and the deep level transient spectroscopy(DLTS)of the samples are measured.All the samples have a rectification characteristic.DLTS signals show two deep levels of E1 and E2.The Gaussian fit curves of the PL spectra at room temperature show three luminescence lines b,c and d,of which b is attributed to the exciton emission.The donor level E1 measured by DLTS and the location state donor ionization energy Ed of the closely neighboring emission lines c and d are correlated.E1 is judged as neutral donor bound to hole emission(D0h).Moreover,the intensity of the PL spectra decreases while the relative density of E2 increases,showing that E2 has the property of a nonradiative center.