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).

射频磁控溅射法制备AZO/p-Si异质结及其性能研究

利用射频磁控溅射法,在p-Si衬底上生长了Al掺杂的ZnO(AZO)薄膜,并进而制备了AZO/p-Si异质结。X射线衍射仪、紫外-可见光分光光度计、四探针测试仪和霍尔效应测试仪测量表明,AZO薄膜具有良好的结晶质量、光学和电学特性。暗态下的I-V测试表明,AZO/p-Si异质结具有较好的整流特性,反向饱和电流为1.29×10-6A,±2V处的正向和反向电流之比为229.41,计算得出异质结的理想因子为2.28。在标准光照下AZO/p-Si异质结呈现出明显的光生伏特效应,这种异质结太阳电池具有2.51%的光电转换效率。

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.

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.

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.

磁控溅射AlN:Mg/ZnO:Al异质结二极管及其光电特性的研究

利用磁控溅射方法,在ITO玻璃基底上分别溅射镁掺杂的氮化铝(AlN:Mg)薄膜、铝掺杂的氧化锌(ZnO:Al或AZO)薄膜,成功制备AlN:Mg/ZnO:Al透明异质结二极管。实验结果表明:AlN:Mg/ZnO:Al异质结具有明显的I-V整流特性,正向开启电压1 V左右,在氙灯光照下,二极管的反向电流在5V偏置时达到3mA。二极管在可见光区域的平均透过率在80%以上,适用于太阳电池的窗口层的研究。

埋栅TCO薄膜的制备及在太阳电池上的应用

提出新型金属埋栅结构来改良透明导电氧化物薄膜(TCO)的光电性能,并分别采用AZO和ITO这2种TCO材料制备和对比3类薄膜(单层TCO薄膜、TCO/金属薄膜/TCO以及TCO/金属栅线/TCO三明治结构的薄膜)的光学和电学性能。本文制备的新型叠层AZO/Mg栅线/AZO和ITO/Ag栅线/ITO结构在300~1200 nm范围内光学透过率保持约在85%,方阻分别降低至1.94和91Ω/□。将ITO/Ag栅线/ITO作为TCO用在n-CdS/p-Si异质结电池上取得了9.31%的效率,相比单层ITO的电池转换效率提高了6.03%。该工作为低方阻、高光学透过率TCO的制备提供了一种行之有效的思路,在光电子器件上也具有一定的应用前景。

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.