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首页> 外文学位 >Low-temperature-grown gallium arsenide photomixers designed for increased terahertz output power.
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Low-temperature-grown gallium arsenide photomixers designed for increased terahertz output power.

机译：低温生长的砷化镓光电混合器，旨在提高太赫兹输出功率。

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摘要

Terahertz radiation can be generated by optical heterodyne conversion in a low-temperature-grown GaAs (IT GaAs) MSM photoconductive switch. In photomixing, two frequency-offset laser beams are used to illuminate voltage biased inter-digitated electrodes, resulting in an AC current at the difference frequency that drives a miniature planar antenna. In this work, the factors limiting photomixer performance have been analyzed and a novel MBE growth structure is presented which provides as much as 5 times greater power in the THz range compared to previous work.; The basic approach used in this work is to reduce the thermal impedance of the photomixer. Because the photomixer active area is so small (10mu m x 10mum) a large temperature gradient is formed within the first several microns of the substrate material and in the LT GaAs itself. The thermal conductivity of the IT GaAs material will, therefore, affect the overall thermal impedance of the photomixer. This implies that a significant improvement in the thermal impedance of the photomixer can be made by reducing the thickness of the LT GaAs layer. A novel layer structure for an improved photomixer is analyzed using finite element analysis for the heat flow simulation and a photoconductive model for the gain calculation. It was found that a large increase in the maximum power should be possible when using a thin LT GaAs layer grown on a relatively thick AlAs layer.; Devices were fabricated on several MBE grown layer structures. Measurement of the photomixers showed record power levels at 850 GHz and 1.6 THz. Compared to a reference sample of 1mum LT GaAs grown directly on GaAs, the maximum power before failure was 4--5 times greater for the devices with an AlAs layer. The optically resonant designs displayed record efficiencies which were 6 times higher than for a sample grown at the same temperature on GaAs.; Analysis of the bias dependence of the external quantum efficiency and the radiated THz power revealed a clear field dependence to the photocarrier lifetime. The increased photocarrier lifetime caused a superlinear I-V characteristic and a super-quadratic bias dependence of the THz power. This field-enhanced lifetime also causes a pronounced peak in the maximum power at failure vs. bias curve. The bandwidth of a broad-band photomixer was decreased at high field, also suggesting a field-dependent lifetime. (Abstract shortened by UMI.)
机译：太赫兹辐射可以通过在低温生长的GaAs（IT GaAs）MSM光电导开关中进行光学外差转换而产生。在光混合中，两个频偏激光束用于照射电压偏置的叉指电极，从而产生具有不同频率的交流电流，从而驱动微型平面天线。在这项工作中，已经分析了限制光混合器性能的因素，并提出了一种新颖的MBE生长结构，与以前的工作相比，该结构在THz范围内提供的功率大5倍之多。这项工作中使用的基本方法是降低光混合器的热阻。由于光混合器的有效面积非常小（10μmx 10mum），因此在衬底材料的前几微米之内以及在LT GaAs本身中都形成了较大的温度梯度。因此，IT GaAs材料的热导率会影响光混合器的整体热阻。这意味着可以通过减小LT GaAs层的厚度来显着改善光混合器的热阻。使用有限元分析进行热流模拟，并使用光电导模型进行增益计算，从而对改进的光混合器的新型层结构进行了分析。已经发现，当使用在相对较厚的AlAs层上生长的薄LT GaAs层时，最大功率的增加应该是可能的。器件是在几种MBE生长层结构上制造的。对光混合器的测量显示出在850 GHz和1.6 THz处的创纪录功率水平。与直接在GaAs上生长的1mum LT GaAs的参考样品相比，具有AlAs层的器件在失效前的最大功率要高4--5倍。光学谐振设计显示出记录效率，该效率是在相同温度下在GaAs上生长的样品的6倍。对外部量子效率和辐射太赫兹功率的偏置依存关系的分析表明，光载流子的寿命存在明显的场依存关系。光载流子寿命的增加导致了超线性I-V特性和太赫兹功率的超二次偏置依赖性。这种磁场增强的寿命还会在故障与偏置曲线上引起最大功率峰值。宽带光混合器的带宽在高场下降低，这也暗示了场依赖的寿命。 （摘要由UMI缩短。）

著录项

  • 作者

    Jackson, Andrew William.;

  • 作者单位

    University of California, Santa Barbara.;

  • 授予单位 University of California, Santa Barbara.;
  • 学科 Engineering Electronics and Electrical.; Physics Condensed Matter.; Engineering Materials Science.
  • 学位 Ph.D.
  • 年度 1999
  • 页码 161 p.
  • 总页数 161
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类 无线电电子学、电信技术;工程材料学;
  • 关键词

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