高质量InGaN的等离子体辅助分子束外延生长和In的反常并入行为

采用射频等离子体辅助分子束外延技术生长得到了In组分精确可控且高质量的In_xGa_1-xN (x ≤ 0.2) 外延薄膜. 生长温度为580 ℃的In_0.19Ga_0.81N薄膜(10.2) 面非对称衍射峰的半高宽只有587弧秒, 背景电子浓度为3.96× 10¹⁸/cm³. 在富金属生长区域, Ga束流超过N的等效束流时, In组分不为零, 即Ga并没有全部并入外延层; 另外, 稍微增加In束流会降低InGaN的晶体质量. 关键词： InGaN 外延薄膜 射频等离子体辅助分子束外延 In 并入 晶体质量     

ITO与Ni和n型GaAs非整流接触的研究

本文报道了氧化铟锡（ITO）分别与金属和半导体的接触电阻率。采用电子束蒸发的手段制备高质量ITO材料。薄膜电阻率为2.32×10-4 Ω?cm,可见光范围透射率为92.8%,禁带宽度为3.804 eV。采用圆点型传输线模型的方法,对ITO/金属和ITO/n型GaAs之间的接触电阻进行了分析。测得ITO与Ni之间最低接触电阻率为2.81×10-6 Ω?cm2 ,ITO与n型砷化镓之间的接触电阻低至7×10-5 Ω?cm2,这是目前所报道的最好的结果。根据以上结果,我们可以确定将ITO应用在GaAs基太阳电池中来提升器件的性能。     

Electroluminescence explored internal behavior of carriers in InGaAsP single-junction solar cell

The internal behaviors of carriers in InGaAsP single-junction solar cell are investigated by using electroluminescence (EL) measurements. Two emission peaks can be observed in current-dependent electroluminescence spectra at low temperatures, and carrier localization exists for both peaks under low excitation. The trends of power index α extracted from excitation-dependent EL spectra at different temperatures imply that there exists a competition between Shockley-Read-Hall recombination and Auger recombination. Auger recombination becomes dominant at high temperatures, which is probably responsible for the lower current density of InGaAsP solar cell. Besides, the anomalous "S-shape" tendency with the temperature of band-edge peak position can be attributed to potential fluctuation and carrier redistribution, demonstrating delocalization, transfer, and redistribution of carriers in the continuum band-edge. Furthermore, the strong reduction of activation energy at high excitations indicates that electrons and holes escaped independently, and the faster-escaping carriers are holes.     

In_(0.53)Ga_(0.47)As/InP雪崩光电二极管响应及电学特性

通过分子束外延生长和开管式Zn扩散方法,制备了低暗电流、宽响应范围的In_(0.53)Ga_(0.47)As/InP雪崩光电二极管.在0.95倍雪崩击穿电压下,器件暗电流小于10nA;-5V偏压下电容密度低至1.43×10~(-8) F/cm~2.在1 310nm红外光照及30V反向偏置电压下,雪崩光电二极管器件的响应范围为50nW~20mW,响应度达到1.13A/W.得到了电荷层掺杂浓度、倍增区厚度结构参数与击穿电压和贯穿电压的关系:随着电荷层电荷密度的增加,器件贯穿电压线性增加,而击穿电压线性降低;电荷层电荷面密度为4.8×10~(12)cm~(-2)时,随着倍增层厚度的增加,贯穿电压线性增加,击穿电压增加.通过对器件结构优化,雪崩光电二极管探测器实现25V的贯穿电压和57V的击穿电压,且具有低暗电流和宽响应范围等特性.     

Transparent conducting indium-tin-oxide (ITO) film as full front electrode in III-V compound solar cell

The application of transparent conducting indium-tin-oxide (ITO) film as full front electrode replacing the conventional bus-bar metal electrode in III-V compound GaInP solar cell was proposed. A high-quality, non-rectifying contact between ITO and 10 nm N⁺-GaAs contact layer was formed, which is benefiting from a high carrier concentration of the terrilium-doped N⁺-GaAs layer, up to 2×10¹⁹ cm^-3. A good device performance of the GaInP solar cell with the ITO electrode was observed. This result indicates a great potential of transparent conducting films in the future fabrication of larger area flexible III-V solar cell.     

Effects of growth temperature on high-quality In0.2Ga0.8N layers by plasma-assisted molecular beam epitaxy

High-quality In_0.2Ga_0.8N epilayers were grown on a GaN template at temperatures of 520 and 580℃ via plasma-assisted molecular beam epitaxy. The X-ray rocking curve full widths at half maximum (FWHM) of (10.2) reflections is 936 arcsec for the 50-nm-thick InGaN layers at the lower temperature. When the growth temperature increases to 580℃, the FWHM of (00.2) reflections for these samples is very narrow and keeps similar, while significant improvement of (10.2) reflections with an FWHM value of 612 arcsec has been observed. This improved quality in InGaN layers grown at 580℃ is also reflected by the much larger size of the crystalline column from the AFM results, stronger emission intensity as well as a decreased FWHM of room temperature PL from 136 to 93.9 meV.     

基于分子束外延生长的1.05 eV InGaAsP的超快光学特性研究

利用分子束外延方法制备了应用于四结光伏电池的1.05 eV InGaAsP薄膜, 并对其超快光学特性进行了研究. 温度和激发功率有关的发光特性表明: InGaAsP材料以自由激子发光为主. 室温下InGaAsP材料的载流子发光弛豫时间达到10.4 ns, 且随激发功率增大而增大. 发光弛豫时间随温度升高呈现S形变化, 在低于50 K时随温度升高而增大, 在50–150 K之间时减小, 而温度高于150 K时再次增大. 基于载流子弛豫动力学, 分析并解释了温度及非辐射复合中心浓度对样品材料载流子发光弛豫时间S形变化的影响.     

Effects of growth temperature on high-quality In_(0.2)Ga_(0.8)N layers by plasma-assisted molecular beam epitaxy

正High-quality In_(0.2)Ga_(0.8)N epilayers were grown on a GaN template at temperatures of 520 and 580℃via plasma-assisted molecular beam epitaxy.The X-ray rocking curve full widths at half maximum(FWHM) of(10.2) reflections is 936 arcsec for the 50-nm-thick InGaN layers at the lower temperature.When the growth temperature increases to 580℃,the FWHM of(00.2) reflections for these samples is very narrow and keeps similar,while significant improvement of(10.2) reflections with an FWHM value of 612 arcsec has been observed.This improved quality in InGaN layers grown at 580℃is also reflected by the much larger size of the crystalline column from the AFM results,stronger emission intensity as well as a decreased FWHM of room temperature PL from 136 to 93.9 meV.     

倍增层厚度对In0.53Ga0.47As/InP雪崩二极管器件特性的影响

利用Zn扩散方法制备了倍增层厚度为1.5,1.0,0.8μm的In_0.53Ga_0.47As/InP雪崩光电二极管(APDs),研究了该器件特性。随着倍增层厚度的增加,器件的贯穿电压和击穿电压均呈现增大趋势。基于Silvaco模拟计算了APD器件的倍增层厚度对电场强度、电流特性、击穿电压与贯穿电压的影响规律,结果表明,随着倍增层厚度的增加,倍增层内电场强度减小,贯穿电压和击穿电压同时增大,与实验结果吻合。进一步研究发现,当倍增层的厚度小于0.8μm时,击穿电压随着倍增层厚度的增加会先减小后增大,贯穿电压则会单调增大。     

1 eV吸收带边GaInAs/GaNAs超晶格太阳能电池的阱层设计

使用In, N分离的GaInAs/GaNAs超晶格作为有源区是实现高质量1eV带隙 GaInNAs基太阳能电池的重要方案之一. 为在实验上生长出高质量相应吸收带边的超晶格结构, 本文采用计算超晶格电子态常用的Kronig-Penney模型比较了不同阱层材料选择下, 吸收带边为1 eV的GaInAs/GaNAs超晶格相关参数的对应关系以及超晶格应变状态. 结果表明: GaNAs与GaInAs作为超晶格阱层材料在实现1 eV的吸收带边时具有不同的考虑和要求; 在固定1 eV的吸收带边时, GaNAs材料作为阱层可获得较好的超晶格应变补偿, 将有利于生长高质量且充分吸收的太阳能电池有源区. 关键词： GaInAs/GaNAs超晶格 Kronig-Penney模型 太阳能电池