Development the semiconductor photorefractive devices employing asymmetric quantum well structures

本研究计画旨在利用非对称耦合量子井结构来改善半导体光折变元件的特性。(1)光谱带宽的改善：飞秒脉冲整形是光折变器件的一个有趣的应用。然而，传统的AlGaAs多量子阱器件的光谱带宽被限制在4 nm波长内。这个带宽太窄，无法处理飞秒脉冲。为了拓宽光谱范围，我们采用了非对称耦合量子阱结构，其中两个不同的量子威尔斯通过薄耦合层耦合。我们可以通过控制威尔斯和耦合层的厚度和深度来调整激子共振的电吸收谱。我们设计并制作了几种非对称量子阱结构，并测量了它们的光折变特性。最后，响应的光谱带宽在波长上展宽到12 nm ...更多信息 长度此外，非对称量子阱结构大大提高了灵敏度。(2)空间分辨率的提高：在p-i-n二极管结构中，通过多个量子阱层纵向施加外部场。在这种几何结构中，光致电荷被捕获在包覆层中。因此，多量子阱层和包覆层之间的能量阶跃在该器件的性能中起着重要作用。通过改变Al和Ga的含量，我们制作了几种具有不同包层势能的器件结构。我们发现能量阶跃的减小提高了器件的空间分辨率。研究发现，熔覆层的电位也会影响其时间行为。(3)新材料GaN：我们证明，在第一次，在半绝缘GaN薄层中的光折变效应在363.6 nm的波长，这是最短的波长，在其中的光折变效应已被证明在半导体。少

The purpose of this research project is to improve the properties of semiconductor photorefractive devices by employing asymmetric coupled quantum well structures.(1) Improvement of spectral bandwidth : Femto-second pulse shaping is one of the interesting applications of photorefractive devices. However, the spectral bandwidth of conventional AlGaAs multiple quantum well devices are limited within 4 nm in wavelengths. This bandwidth is too narrow to handle femto-second pulses. In order to broaden the spectral region, we have employed an asymmetric coupled quantum well structure, where two different quantum wells are coupled through thin coupling layers. We can tailor the electro-absorption spectrum of excitonic resonance by controlling the thickness and depth of wells and coupling layers. We have designed and fabricated several asymmetric quantum well structures and have measured the photorefractive properties. Finally, the spectral bandwidth of response is broadened up to 12 nm in wav … More elength. Moreover, the asymmetric quantum well structure improved the sensitivity substantially.(2) Improvement of spatial resolution : In p-i-n diode structures, the external field is applied longitudinally through the multiple quantum well layers. In this geometry, photo-induced charges are trapped in cladding layers. Therefore, the energy step between the multiple quantum well layers and the cladding layers plays an important roll in the performance of this device. We have fabricated several device structures that have different potential energy of cladding layers by changing the fractions of Al and Ga. We found that the reduction of energy step improves the spatial resolution of device. It is found that the temporal behavior is also influenced by the potential of cladding layer.(3) New material GaN : We demonstrated, at the first time, the photorefractive effect in a semi-insulating GaN thin layer at the wavelength of 363.6 nm, which is the shortest wavelength at which the photorefractive effect has ever been demonstrated in semiconductors. Less