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to draw definite conclusions, these results suggest that the steady-state concentration of arsine entering the reactor may be somewhat reduced due to absorption effects in the molecular sieve column.A possible area for further investigation is the effect of lowering the temperature of the molecular sieves to a point where dopant impurities may be more effectively absorbed. However arsine absorption effects are also expected to be more pronounced at lower temperatures. (The condensation temperature of arsine in the 4% mixture is ca. -113~ (12). We have not attempted to pursue this approach. Also, we have not examined other molecular sieve structures. ConclusionWe have grown InGaAs samples by hydride VPE using a column of Type 4A molecular sieves in the arsine line. These samples did not differ significantly either in background carrier concentration or in Hall mobility from corresponding samples grown using untreated arsine. We therefore conclude that these molecular sieves are not effective at room temperature in removing dopant impurities from the 4% arsine-hydrogen mixture used. AcknowledgmentsWe wish to thank C. M. Stiles for SEM measurements and R.F. Kopf for Hall effect measurements. We also thank J. Long, D. Coblentz, and J. L. Zilko for helpful discussions and W. D. Johnston, Jr. and M. A. DiGiuseppe for advice and encouragement.