ABSTRACTThe lack of high-temperature thermodynamically stable contacts has been a limiting factor for III-V compound semiconductor metallization. The instability of metal/semiconductor contacts at higher temperatures arises due to factors such as thermodynamic instability at the interface, lack of chemical inertness especially to oxygen containing ambients and a large lattice mismatch to the substrate. Our studies of two rare-earth compounds, dysprosium phosphide (DyP) and dysprosium arsenide (DyAs), demonstrate their potential to address the above problems. The growth and characterization of these two materials and their heterostructures will be presented.Both the DyP and DyAs epilayers were grown using MBD. DyP has an excellent room temperature lattice match to GaAs with a mismatch of about 0.01%, whereas DyAs has a lattice mismatch to GaAs on the order of about 2.4%. Consistent high quality DyP and good quality DyAs epilayers, as characterized by TEM, XRD, AES and AFM were obtained for growth temperatures between 500°C and 600°C. The growth rate was about 0.5 μm/hr and and the RMS roughness of the epilayer surface was typically about 0.5 nm and 1.3 nm for Dyp and DyAs, respectively.Electrical characterization of DyP and DyAs include variable temperature Hall measurements, four point probe, TLM, I-V and C-V measurements. Results show that both DyP and DyAs epilayers are n-type with electron concentration between 3–4 × 1020cm−3 and 2–3×1021cm−3, respectively. The room temperature mobility and resistivity of DyP are 300 cm2/Vsec and 60 μ Ω cm, respectively. The room temperature mobility of DyAs is about 50 cm2/Vsec. DyP forms a Schottky barrier to GaAs with a barrier height of 0.81eV and DyAs forms a weak Schottkyt barrier to GaAs. All relevant data will be presented along with schemes for using DyP and DyAs as potential interconnects to III-V compound semiconductors.
Crystal Chemistry and Stability of Hydrated Rare-Earth Phosphates Formed at Room Temperature
