Alternative group V sources for growth of GaAs and AlGaAs by MOMBE (CBE)

Abstract

We have investigated the use of phenylarsine (PhAsH 2) and trisdimethylaminoarsenic (DMAAs) as potential replacements for AsH 3 during growth by metalorganic molecular beam epitaxy (MOMBE), alternatively known as chemical beam epitaxy (CBE). PhAsH 2 was found to decompose rather inefficiently on the surface at a growth temperature of 525°C. However, GaAs and AlGaAs growth rates up to ∼ 95 Å/min could still be obtained at this temperature without incurring any degradation in morphology. The hydrogen generated by the decomposition of the PhAsH 2 did not appear to getter carbon from the surface as both GaAs and AlGaAs grown from PhAsH 2 contained ten times more carbon than layers grown under the same flux of AsH 3. By contrast, DMAAs was found to decompose readily on the wafer surface allowing growth rates up to 220 Å/min and growth temperatures as low as 375°C. Furthermore, DMAAs was found to getter carbon more efficiently than cracked AsH 3, probably as a result of tertiary amine formation at the wafer surface. As a result, comparable carbon backgrounds were obtained at 525°C from either TEG or TMG. By using these sources in tandem, it appears that AsH 3 may no longer be required for growth of GaAs or AlGaAs by MOMBE. In addition, these sources allow new flexibility for selective growth as well. The stability of PhAsH 2 allows for selective deposition of pAlGaAs even at temperatures as low as 525°C. While the same effect is not observed for GaAs growth from TEG at these temperatures, it is possible through the use of DMAAs to deposit high purity GaAs selectivity from TMG since the DMAAs getters the carbon without inducing deposition on the mask. Thus the use of PhAsH 2 and DMAAs will allow selective deposition of device structures such as Pnp HBTs at their optimum growth temperature of ∼ 525°C.