GaAs Liquid Phase Epitaxy
Liquid phase epitaxy is a crystal growth technique involving the near equilibrium growth of GaAs and other compounds from a saturated solution that is placed in contact with a polished substrate, generally GaAs. Just before or just after the surface of the substrate has been coated, the temperature is lowered from the equilibrium temperature at a controlled rate bringing on super saturation of the solution and leading to precipitation and epitaxial growth of the dissolved material onto the substrate.
The basic idea of LPE technology is not revolutionary in principle but in reality it is very sensitive to production-applied handling and is thus regarded as extremely demanding in industrial deployment. Clifton has successfully implemented the industrially challenging Liquid Phase Epitaxy (LPE) processing technology, solved all its technical hurdles, improved the technology, achieved control over the gallium arsenide crystal growth process and deployed it into production of high-voltage gallium arsenide p-i-n structures.
Capabilities of LPE technology
The improved LPE technology permits control of the p-i-n EPI layer thickness from 10 to 300µm
, and i-region thickness from 3 to 100 µm, in which, high quality, homogeneous layers can be produced for specific electrical characteristics. The doping profile of Clifton`s epitaxial structures enables high voltage avalanche breakdown values of the p-i-n junction to achieve up to 1600 V. The high level of breakdown voltage is achieved by growing the lightly doped p-i-n layer in a single LPE process when the high voltage p-i-n junction is formed through the compensation of acceptor impurities with donors in a controlled epitaxial cooling. Through this process, the net carrier concentrations near the top surface of the epi-layer do not exceed 1016cm-3 and the net carrier concentrations in the i-region do not exceed 1012cm-3. LPE enables control of the dopant distribution and region thickness amongst the p-i-n layer within the structure yielding much of high-power GaAs structure`s electrical parameters.
The production of our structures and die undergo an in depth process which includes:
- surface layer crystal growth (p-i-n and n+ epitaxy)
- metallization (vacuum evaporation to create a Ohmic contact layer)
- photolithography (printing a frame for etching)
- passivation (applying a side protection for junction layer)
- checking and testing of die
All steps are preceded by chemical and/or mechanical treatment. A quality control system is in place throughout the whole production chain to guarantee excellency of the final production.