III-V TERNARY SEMICONDUCTOR HETEROSTRUCTURES - THE CHOICE OF AN APPROPRIATE COMPOSITIONAL ANALYSIS TECHNIQUE

The composition of ternary III-V semiconductor heterostructures can now be measured in a number of ways. Conventional spectroscopic probe techniques are inappropriate for fine (nanometer scale) heterostructures: Here, those transmission electron microscopy techniques which are appropriate, are compared emphasizing that different alloy systems often require different approaches. The three representative methods discussed in detail are kinematic convergent beam diffraction, 200 dark field intensity measurement, and [001] bright field thickness fringe matching. Dark field intensity measurement is found to be the most sensitive analytical method for many alloys, but the accuracy that may be achieved by thickness fringe matching is generally little worse, and sometimes better. Those convergent beam diffraction techniques which rely on lattice parameter measurement would not appear to be particularly useful except for the purposes of distinguishing nonunique interpretations of other measurements. It is also noted that no technique currently available is capable of measuring the composition of Al(x)Ga(1-x)Sb alloys to an accuracy of better than +/- 0.05 in x, so that further technique development will be required if heterostructures in this alloy system are to be studied seriously.