Interfacial structures and electrical properties of titanium and germanium/nickel metallizations to indium phosphide (thin films)

The literature concerning the principles of ohmic contact formation and properties of InP is comprehensively reviewed. Interfacial reactions that occur during annealing in three metallization systems, i.e., Ti(100 nm)/InP, (annealed in forming gas: 95% N{dollar}sb2{dollar} + 5% H{dollar}sb2),{dollar} Ni (50 nm)/InP, (annealed in vacuum) and Ge (52.5 nm)/Ni(25 nm)-InP, (annealed in forming gas), were characterized using transmission electron microscopy (TEM) and related techniques. Thin films for the three systems were deposited by electron beam evaporation onto {dollar}{lcub}langle{rcub}001{lcub}rangle{rcub}{dollar} oriented InP.; Initial interfacial reactions between Ti thin films and InP were detected at 325{dollar}spcirc{dollar}C. which resulted in the formation of metallic In and TiP. TiP formation was limited by kinetics at low temperatures and much of the P released during InP decomposition was lost to the atmosphere. The amount of TiP formation increased with increasing temperatures and TiP was the only Ti-P phase detected. No In-Ti compound formation was detected in any sample studied.; For Ni/InP metallizations, initial annealing ({dollar}<{dollar}250{dollar}spcirc{dollar}C) led to the formation and growth of an amorphous ternary phase (Ni{dollar}sb{lcub}approx3{rcub}{dollar}InP) at the Ni/InP interface. This was followed by crystallization of the amorphous ternary phase (250-300{dollar}spcirc{dollar}C) to Ni{dollar}sb2{dollar}InP and Ni{dollar}sb2{dollar}P. Annealing at 500{dollar}spcirc{dollar}C resulted in the decomposition of Ni{dollar}sb2{dollar}InP to Ni{dollar}sb2{dollar}P and metallic In, which subsequently oxidized forming In{dollar}rmsb2Osb3.{dollar}; In the Ge/Ni-InP system, all amorphous ternary phase similar to the one in the Ni/InP system formed between Ni and InP ({dollar}<{dollar}250{dollar}spcirc{dollar}C). The amorphous ternary phase decomposed at 250{dollar}spcirc{dollar}C forming a Ni{dollar}sb2{dollar}P-type compound, which then transformed to GeNi. The GeNi is laterally uniform between 250 and 350{dollar}spcirc{dollar}C. High temperature annealing resulted in a roughened InP interface and further InP decomposition. Specific contact resistances were measured using a modified transmission line method (TLM). Values as low as {dollar}10sp{lcub}-6{rcub}Omega{dollar}-cm{dollar}sp2{dollar} have been obtained. Microstructural changes have been correlated with the electrical results.