Growth and characterization of low-temperature grown gallium arsenide and resonant cavity structure

There is a need for photodiodes which can operate at high speeds (30 GHz or more) and at high efficiencies (greater than 70%). These photodiodes can be used as receivers in communication networks which use fiber-optic links for long distance transmission. We studied several novel photodiodes, including a structure which is capable of detecting two wavelengths. These devices were optimized for performance in terms of intrinsic speed and device efficiency. We used a resonant cavity structure which employing a thin absorption region between two mirrors. The cavity and mirrors were designed for optimal efficiency at an operating wavelength. The thin absorption region ensures that the device is not transit time limited, which results in a high speed of operation.;Low-temperature grown GaAs has some interesting material properties which make it useful for a variety of device applications. The high resistivity of this material makes it an excellent choice as an isolation buffer region. This material also exhibits photoresponse to sub-bandgap illumination. Although the absorption efficiency of this layer to sub-bandgap photons is low (less than 2%), we have studied ways to optimize the photoresponse of this material using growth variables and resonant cavity structures. The photoresponse behavior of the material when alloyed with In was also studied as a function of InGaAs alloy concentration. All these studies helped us in understanding some of the basic physics of the low-temperature grown GaAs.