Thin Solid Films, Vol.306, No.2, 266-270, 1997
Ultrahigh vacuum atomic layer epitaxy of Cd1-xMnxTe layers grown on ZnTe/GaAs(100) substrates : reflection mass spectrometry studies
Simultaneous reflection mass spectrometry (REMS) and reflection high energy electron diffraction (RHEED) measurements of the surface kinetic and structural parameters, respectively, governing the UHV ALE growth of Cd1-xMnxTe films are reported. A set of six experiments have been performed. Three of them concerned Cd1-xMnxTe UHV ALE, and one Cd1-xMnxTe MBE growth. For comparison, one experiment was also performed concerning UHV ALE of Cd1-xZnxTe and one concerning UHV ALE of CdTe, with two sequent cation deposition pulses. The REMS signals for Cd+ cations during the deposition and 'dead' times of the ALE cycle were measured. RHEED patterns were also recorded to control the surface reconstruction of the epilayer during different deposition stages of the ALE cycle. An interesting phenomenon was observed in the REMS Cd+ signal behaviour during the ALE growth of Cd1-xMnxTe and Cd1-xZnxTe. It consists in an evident increase of the intensity of this signal occurring in cases when both cation elements (Cd + Mn or Cd + Zn) are impinging onto the substrate surface simultaneously. These changes in Cd+ REMS signals (15% and 5% in the cases of Cd + Mn and Cd + Zn simultaneous deposition, respectively) have been attributed to effects of mechanical impacts between 'hot' Mn and a bit 'cooler' Zn atoms with weakly bound 'cool' Cd atoms which are thermally accommodated to the substrate surface. The same mechanism, namely mechanical impact of 'hot' Mn atoms with 'cool' Cd atoms is believed to be responsible for the measured differences in chemical composition of the ternary compound Cd1-xMnxTe, when grown by MBE (x = 0.4) or UHV ALE (x = 0.06), at the same growth parameters applied.