Application of Iron-doped GaAs to Optically-Controlled Variable Resistors

第一年，利用扩散铁深受主对施主的过补偿，制备了pi/n^+结构的GaAs二级管。同时对扩散区的铁含量进行了分析。根据扩散温度650-900ﾟC的不同，深度剖面非常平坦，浓度范围从10^&lt；15；A/cm^3到10^&lt；17；A/cm^3，这一结果已发表在日本应用物理杂志上。通过铁扩散选择性反转电导类型，成功地制备了pi/n^+/pi结构的器件。第二年，用体材料和外延材料制备了低铁浓度的二极管，并测试了它们的伏安特性。器件的漏电流低至1×10~(-9)A/cm~2，击穿电压在500V以上，但结特性与起始材料有很强的依赖关系。这些考虑导致了一种pi/n^+/pi台面结构，在表面上有一对中间电极和一个背电极来暂时偏置器件。在偏置后，表面pi-layr的电阻变化了10倍以上，在弱光照下恢复到初始值。由于层状结构中的电荷存储引起的高阻状态在几分钟内衰减，这限制了其在动态工作中的应用，为了进一步扩展其适用性，必须通过减少泄漏电流来增加电荷存储时间。此外，目前的研究表明，类似的结构可能是超高速光电探测器的候选者，很快就会进行研究。

In the first year, GaAs diodes of pi/n^+ structure were fabricated by use of overcompensation of donors by diffused iron deep acceptors. Meanwhile, iron concentrations in the diffused regions were analyzed. The depth profiles are remarkably flat and the concentration ranges from 10^<15> to 10^<17>A/cm^3 depending on the diffusion temperature of 650-900ﾟC,which result have been published in the Japanese Journal of Applied Physics. Selective inversion of conductivity type by iron-diffusion was successful to produce a pi/n^+/pi structure for the present device.In the second year, diodes with lower iron concentration were fabricated from bulk and epitaxial GaAs materials, and their current-voltage characteristics were examined. Leakage current as low as 1x10^<-9> A/cm^2 and high breakdown voltage over 500 V were realized, but the junction characteristics were found to depend strongly on the starting material. These considerations resulted in a pi/n^+/pi mesa structure with a pair of interdital electrodes on the surfaces and a back electrode to temporarily bias the device. The resistance of the surface pi-layr changes by a factor over 10 after the structure is biased, and recovers to the initial value when weakly illuminated. The high-resistance state caused by the stored charge in the layred structure decays in a few minutes, which limits its application to dynamic operations.To further extend its applicability, the charge storage time must be increased by reducing the leakage current. Also, the present study suggests that a similar structure may be a candidate for an ultra-fast photodetector, which will be under investigation soon.