Liquid Phase Epitaxy
Liquid phase epitaxy (LPE) is a crystal growth technique that dates back to the 1960s. Although seldom used today, LPE was the enabling technology for many of the most critical compound semiconductor technologies that are still prevalent today (including the AlGaAs/GaAs heterojunction bipolar transistor, high efficiency solar cells, CW lasers, and LEDs). While much of the industry and research work in compound semiconductors has moved on to modern growth techniques such as molecular beam epitaxy (MBE) and metalorganic chemical vapor deposition (MOCVD), LPE still provides great value when performing early investigations. Some of the primary benefits include the ability to obtain ultra-high quality material due to the near-equilibrium growth process, relatively high growth rates for quick materials characterization studies, and low capital expense (important for early-stage research!). Of course, there are difficulties that some naysayers like to point out, such as difficulty in run-to-run control, attaining precise layer thicknesses (down to the nm level), and limited ability for fine-tuning. But, that’s all fine by me. In any case, there is still ample room for all growth methods to work in harmony, and our LPE system is one-of-a-kind for doing investigations in visible wavelength optoelectronic devices.
The Bottom Line
Remember that experiment you did in grade school to make rock candy? I basically do that, but with higher-priced materials. Why? It turns out that the quality of the newly-grown material (grown by LPE) is superior to that of other more highfalutin methods. This allows for neat investigations of various physical properties that are important for solar cells and light emitters.