Abstract
This paper describes the design, fabrication and characteristics of a new type of near-infrared (NIR) photodiodes. The photodiode consists of a lattice-mismatched GaInAs light-absorbing layer, a very thin InP/InAsP cap layer and a InAsP strained superlattice (SSL) buffer layer. The very wide wavelength spectral response over a wavelength range from 0.6 to 2.1μm and low dark current have been achieved for the first time using this specially designed photodiode structure. The newly developed InAsP SSL structure were successfully used to realize the about fivefold reduction in the thickness of the buffer layer. This also demonstrates the feasibility of fabricating state-of-art lattice-mismatched GaInAs photodiodes grown by metalorganic vapor-phase epitaxy. A shallow pn junction through the very thin cap layer was formed using the new Zn diffusion technique.
The mean detectivity D* at 300K was higher than 1011cmHz-1/2W-1 in the wavelength range from 1 to 2μm. The photodiode mounted on a cooling unit in a hermetically-sealed package with a glass window can operate with D*>1012cmHz-1/2W-1 from 1.3 to 2.1μm. These photodiodes are the preferred devices in a wide range of NIR system, including remote sensing, gas analysis, and pollution detection. They are also ideal for NIR spectroscopic applications (such as FT-NIR system) requiring wide-wavelengthspectral data to perform chemometric analysis.
