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     

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.     

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.     

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     

Strain relaxation and optical properties of etched In_0.19Ga_0.81 N nanorod arrays on the GaN template

InGaN/GaN epilayers,which are grown on sapphire substrates by the metal-organic chemical-vapour deposition(MOCVD) method,are formed into nanorod arrays using inductively coupled plasma etching via self-assembled Ni nanomasks.The formation of nanorod arrays eliminates the tilt of the InGaN(0002) crystallographic plane with respect to its GaN bulk layer.Photoluminescence results show an apparent S-shaped dependence on temperature.The light extraction efficiency and intensity of photoluminescence emission at low temperature of less than 30 K for the nanorod arrays are enhanced by the large surface area,which increases the quenching effect because of the high density of surface states for the temperature above 30 K.Additionally,a red-shift for the InGaN/GaN nanorod arrays is observed due to the strain relaxation,which is confirmed by reciprocal space mapping measurements.     

Strain relaxation and optical properties of etched In0.19Ga0.81N nanorod arrays on the GaN template

InGaN/GaN epilayers,which are grown on sapphire substrates by the metal-organic chemical-vapour deposition(MOCVD) method,are formed into nanorod arrays using inductively coupled plasma etching via self-assembled Ni nanomasks.The formation of nanorod arrays eliminates the tilt of the InGaN(0002) crystallographic plane with respect to its GaN bulk layer.Photoluminescence results show an apparent S-shaped dependence on temperature.The light extraction efficiency and intensity of photoluminescence emission at low temperature of less than 30 K for the nanorod arrays are enhanced by the large surface area,which increases the quenching effect because of the high density of surface states for the temperature above 30 K.Additionally,a red-shift for the InGaN/GaN nanorod arrays is observed due to the strain relaxation,which is confirmed by reciprocal space mapping measurements.