A photoresist etch mask process has been developed for the etching of (110) direction, (111B) faceted v‐grooves in normalInP (001) wafers. Etching rates are measured about 0.083 and 0.042 μm/s for etching depth and undercutting, respectively. The undercutting mechanism is discussed. The deterioration of the etching solution and the resist mask have been studied.

A photoresist etch mask process has been developed for the etching of v‐grooves in normalInP (001) for channeled substrate laser growth. The relationship between the photoresist (PR) mask undercutting and the dehydration bake temperatures, the postbake temperatures, and the photoresist thicknesses were studied. The native oxide growth during the bake processes was believed to give the extra large undercut.

Nonalloyed Ohmic contacts of evaporated Pt/Ti to p-InGaAsP (λg=1.3 μm) with different Zn doping levels ranging 5×1018–2×1019 cm−3 have been fabricated by rapid thermal processing. These contacts showed Ohmic behavior prior to any heat treatment with a specific contact resistance of 4×10−3 Ω cm2 for the lowest doping level and 1×10−4 Ω cm2 for the highest level. A decrease in the specific resistance was achieved by supplying rapid thermal processing to the contacts, while the lowest values were observed on all the contacts as a result of heating at 450 °C for 30 sec. The lowest resistance of 1×10−6 Ω cm2 was achieved at the contact that was formed on the 2×1019 cm−3 Zn-doped InGaAsP layer. Measurements of the conduction activation energy yields a good linear dependence of the specific resistance on temperature in all the contacts as deposited and after the different heat treatments. The higher the doping level and the rapid thermal processing temperature up to 450 °C, the lower the activation energy, which may suggest an increase in the tunneling carrier transport mechanism contribution at the expense of the thermionic-emission one. The morphology and microstructure of these contacts were not influenced by the variations in the Zn doping concentration.

Very low resistance nonalloyed ohmic contacts of Pt/Ti to 1.5×1019 cm−3 Zn-doped In0.53Ga0.47As have been formed by rapid thermal processing. These contacts were ohmic as deposited with a specific contact resistance value of 3.0×10−4 Ω cm2. Cross-sectional transmission electron microscopy showed a very limited interfacial reacted layer (20 nm thick) between the Ti and the InGaAs as a result of heating at 450 °C for 30 s. The interfacial layer contained mostly InAs and a small portion of other five binary phases. Heating at 500 °C or higher temperatures resulted in an extensive interaction and degradation of the contact. The contact formed at 450 °C, 30 s exhibited tensile stress of 5.6×109 dyne cm−2 at the Ti/Pt bilayer, but the metal adhesion remained strong. Rapid thermal processing at 450 °C for 30 s decreased the specific contact resistance to a minimum with an extremely low value of 3.4×10−8 Ω cm2 (0.08 Ω mm), which is very close to the theoretical prediction.

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