Intrinsic SEU Reduction from Use of Heterojunctions in Gallium Arsenide Bipolar Circuits

Use of GaAs/AlGaAs heterojunctions at the base emitter junction in MBE-type GaAs bipolar circuits reduces the thickness of the SEU sensitive volume associated with each transistor to about 0.2¿m. This results in a sharply reduced charge collection and a correspondingly sharp reduction in SEU sensitivity even for low values of the critical charge. The effect is illustrated with an HI2L gate array developed at Texas Instruments in which shift registers do not exhibit upsets upon exposure to heavy ions with LET values of up to 20 MeVcm2/mg(GaAs) which is equivalent to over 30 MeVcm2/mg(Si). A low-current version of the same shift registers exhibits an upset cross section of only 3 E-13 cm2/bit at an LET of 20 MeVcm2/mg and zero at 11 MeVcm2/mg(GaAs). Neither of the devices could be upset by exposure to 63 MeV protons at a fluence of 1E + 12 p/cm2 in agreement with the predictions of the CUPID codes.