I wanted to improve an existing infrared lamp heater in a so called horizontal geometry MOCVD reactor, where MOCVD stands for metal-organic compound vapour deposition. This is an epitaxy process for the fabrication of a variety of semiconductor heterostructures. The reactor stands in the Institute of Solid State Physics of Technical University Berlin and is used for research purposes described on their homepage: http://sol.physik.tu-berlin.de/htm_group/research/pg_nanostrukturen_e.html

The reactor comes from the company Aixtron AG, and you will find details on it by visiting their page, http://www.aixtron.com and navigating to Products&Services / Products / AIX 200/4.

In my ZEMAX files (attached at the end of this article) you find a big glass tube around which six reflecting elements are arranged. In real life, this glass tube and the surrounding lamp heater look similar to that shown in http://www.fbh-berlin.de/images/downl/300/Horizontalreaktor.jpg (this picture is copyright Ferdinand-Braun-Institute).

The glowing item in the middle of the reactor tube is a graphite block, called the susceptor, and has the shape shown in the ZEMAX files by the detector surfaces:

The circular object in the center is a rotating tray carrying three circular subtrays (not really visible in this graphic). Those accommodate one 2” wafer each. On the wafer, the epitaxial layers will be deposited by a flow of so called precursor gases of metal-organic compounds. The wafers are heated by the lamp heater beneath the susceptor, and their temperature is a crucial parameter in the entire process. It is of interest to be able to (i) rapidly change the temperature and (ii) reach a high end temperature.

The Aixtron heater works well, but still has potential for improvement, as it is suited to a variety of Aixtron reactors. We wanted to optimize it for use in our specific application. Aixtron use parabolic reflectors which are good but not optimal for our specific task. Obviously, elliptic mirrors would enhance the radiation transfer to the detector surfaces representing the bottom side of the graphite susceptor. This was my task!