Title :
Determining the effectiveness of HBT emitter ledge passivation by using an on-ledge Schottky diode potentiometer
Author :
Ma, Pingxi ; Zampardi, Peter ; Zhang, Liyang ; Chang, M.F.
Author_Institution :
Dept. of Electr. Eng., California Univ., Los Angeles, CA, USA
Abstract :
A Schottky diode, which contacts the emitter ledge directly, is used as a potentiometer to monitor the effectiveness of the emitter/base junction passivation in GaAs based heterojunction bipolar transistors (HBTs). The function and mechanism of this on-ledge potentiometer are carefully analyzed and modeled. With this apparatus, the emitter ledge potential (V/sub Ledge/) can be measured as a function of the base-emitter bias voltage V/sub BE/. By relating V/sub Ledge/ to V/sub BE/. We are capable of quantifying the extent of the ledge depletion down to a few angstroms (<10 /spl Aring/) in precision. The excellent detectivity of the potentiometer makes it a very powerful tool in the diagnosis of HBT problems in both operation and long-term reliability. These problems have not been detectable or distinguishable with prior techniques.
Keywords :
III-V semiconductors; Schottky diodes; gallium arsenide; heterojunction bipolar transistors; passivation; potentiometers; semiconductor device measurement; GaAs; GaAs heterojunction bipolar transistor; Schottky diode potentiometer; emitter ledge passivation; Analytical models; Equivalent circuits; Gallium arsenide; Heterojunction bipolar transistors; Monitoring; Passivation; Potentiometers; Resistors; Schottky diodes; Voltage;
Journal_Title :
Electron Device Letters, IEEE