In metal organic vapor phase epitaxy (MOVPE), it is well known that the optical and electrical properties are strongly affected by factors of film quality such as the thickness uniformity, the impurity incorporation, the existence of vacancy. The engineers and scientists with well-skilled techniques are trying to avoid the undesired results. However, the optimization process of MOVPE growth conditions is subjectively judged by the expert's own experience and knowledge. Therefore, it is very hard to share his/her skill.
In this paper, we investigate the effect of MOVPE growth parameters on GaAs film quality, and then adapt analytic hierarchy process (AHP) approach to evaluate quantitatively and qualitatively expert's skill in order to obtain high quality MOVPE-GaAs layers.We believe that this approach of AHP would be applicable for analyzing and digitalizing expert's skills, and transferring them to non-skilled people.
In fundamental AHP method, the structure of three level hierarchy must be formed. The first level is over all objective of achievement of high quality GaAs using MOVPE. The second level is the four factors or criteria that contribute to the objective. Here, we focus on four major quality factors such as the thickness uniformity, the abrupt interface, the filling of vacancy and the accuracy of stoichiometry.
The third level consists of five elements or alternatives that are to be evaluated in terms of the criteria on the second level. With regard to our consideration, the alternatives, which affect the GaAs film quality, are four MOVPE growth parameters of the reactor pressure, the substrate temperature, carrier gas supply rate and V/III ratio.
One of the calculating result is shown below. By doing matrices of pairwise comparison of each element based on expert's answer, the highest value of weight value is V/III ratio which estimated to be 0.411. This is followed by the terms of Substrate Temperature (weight: 0.309), Reactor Pressure (weight: 0.198), and Carrier Gas Supply Rate (weight: 0.082). These results indicate that an expert think V/III ratio as the primary adjusting parameter. If expert cannot satisfy the film quality, he would change the substrate temperature as the secondary adjusting parameter.
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