AuBe/p-InGaAsP Contact Formed By Rapid Thermal Processing

01 January 1989

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The alloyed ohmic contact of AuBe (1% by weight Be) to 5 . 10 sup (18) cm sup (-3) Zn doped p-InGaAsP (lambda sub g = 1.3micron) was fabricated by rapid thermal processing and its performance compared to that of the contact formed by conventional furnace heating. The specific contact resistance decreased from a value of 4.9 . 10 sup (-4) ohm cm sup 2 as-deposited to a value of 4.9 . 10 sup (-7) ohm cm sup 2 as result of rapid thermal processing at 420C for 30 sec. This value was much lower than the value of 3.9 . 10 sup (-6) ohm cm sup 2 obtained as a result of furnace heat treatment at 420C for 10 min. Rapid thermal processing at higher temperatures caused a sharp increase of the specific contact resistance. Auger depth profiling indicated that this degradation of the contact electrical performance at formation temperatures of 450C and above results were caused by strong localized interactions between the AuBe and the InGaAsP and outdiffusion of all the quaternary elements toward the surface of the contact. The effective stress in the alloyed layer, normalized to the initial AuBe thickness of 80nm, is tensile with a value of 7x10 sup 9 dyne cm sup (-2), and is much less sensitive to the alloying parameters (time and temperature) than is the contact resistance.