It has generally been recognized that sources of the highest purity facilitate growth of loP and InAlAs with excellent optical and electrical characteristics. The mobility, photoluminescence linewidths, X-ray linewidths, impurity levels, and ultimately device results have been evaluated for two different hydride purity levels. It was found that each of the above characteristics was affected by improved arsine and phosphine purity. The 77 K mobility of lnP increased by a factor of 2 and the InAlAs silicon doping efficiency increased by a factor of 5. Accompanying improvement in device performance, notably the peak to valley ratio of resonant tunneling structures has been observed.