A gigahertz cryogenic HEMT pseudorandom number generator chip set

A 1-GHz high electron mobility transistor (HEMT) chip set for a cryogenic pseudorandom number generator subsystem that has enhancement/depletion (ED) direct-coupled FET logic (DCFL) circuits and operates at liquid nitrogen temperature is described. Using HEMT circuitry at cryogenic temperatures has several advantages. The DC characteristics of the HEMT are improved. The resistance of interconnecting metal at 77 K is about one-third that at room temperature. This minimizes interconnection delay, which is defined by the RC time constant, and simplifies the layout of power and ground lines. Heat is removed from the IC by immersing the bare chip in liquid nitrogen. A 32-b pseudorandom number generator for an external unit of a scientific computing system demonstrates the feasibility of the HEMT-IC-based computer operating at 77 K.<
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