Characterization of high-purity arsine and gallium arsenide epilayers grown by MOCVD

Impurities present in the metal organic chemical vapor deposition (MOCVD) process gases and precursors can have a significant effect on the performance of III–V compound semiconductor devices. High-purity arsine purified using chemical, adsorption and distillation techniques, has been characterized for impurities by using high sensitivity gas analysis methods and low temperature photoluminescence (PL) of GaAs epilayers. Permanent gas, hydrocarbon and dopant impurities can all be removed using these purification methods to below the detection limit of instrumentation (low nmol mol−1–pmol mol−1, depending on method). Capability to remove water vapor to single digit nmol mol−1 levels is also demonstrated and cylinder depletion studies show that gas-phase arsine, with consistently low H2O, can be delivered from the cylinder, even well after phase break. Low temperature PL measurements are made on 10 μm GaAs/GaAs grown with three different arsine sources. Well-resolved near-band emission characteristics of high-purity n-type GaAs is obtained with high-purity distilled arsine. PL of epilayers grown with less pure arsine show the presence of Ge as well as elevated levels of Mg and Zn, incorporated from the trimethylgallium. The incorporation of O from an arsine cylinder containing H2O at 200 nmol mol−1 results in reduced full width at half maximum (FWHM) of the near-band emission and decreased (D0, X) and (F, X) intensity, highlighting the importance of minimizing H2O impurity.