A Low 1/f Noise and High Reliability InP/GaAsSb DHBT for 76 GHz Automotive Radars

To develop a low 1/f noise and high reliability InP/GaAsSb DHBT, experimental analyses on the recombination current have been carried out. The results show that the recombination current that can affect 1/f noise and reliability originates from the surface of the base. We have optimized the ledge and passivation film on the base surface of InP/GaAsSb DHBT. The optimized DHBT offers 7 dB lower 1/f noise level than the non-optimized DHBT. Additionally, in the high temperature burn-in test, no degradation has been induced even after 1,000 hr. It can satisfy the criterion of automotive radars. The W-band oscillator with the optimized DHBT delivers a remarkably low phase noise of -107 dBc/Hz at 1MHz-offset. This phase noise is 10 dB lower than that of the non-optimized HBT oscillator. These results experimentally confirm that decreasing 1/f noise is effective for the design of a low phase noise oscillator using InP/GaAsSb DHBT. To our knowledge, this is the first report to reveal that the base surface structure of InP/GaAsSb DHBT is a key factor in the improvement of reliability and phase noise.