Memory effect of Ge in III–V semiconductors

Epitaxial growth of germanium is attractive for Ge/III–V hetero devices such as multi-junction solar cells. We investigated the growth of Ge with iso-butyl germane (IBGe) as germanium source and found a strong memory effect in our AIX2600-G3 metalorganic vapor phase epitaxy (MOVPE) reactor. The germanium background led to a higher n-type doping of i-GaAs and strongly reduced the photoluminescence (PL) intensity of Al0.3Ga0.7As and Ga0.5In0.5P. With secondary ion mass spectroscopy (SIMS) the quantity of Ge in Al0.3Ga0.7As could be determined to be in the range of 2×1017 cm−3, whereas a Ge-atom concentration in Ga0.5In0.5P of up to 2×1018 cm−3 was measured. The memory effect could be eliminated by changing all contaminated parts inside the MOVPE reactor.