P-N-I-P and N-P-I-N Junction Transistor Triodes

P-N-I-P and N-P-I-N Junction Transistor Triodes By J. M. EARLY (Manuscript received March 18, 1954) Theory indicates that the useful frequency range of junction transistor riodes may be extended by a factor of ten by a new structure, the p-n-i-p, which uses a thick collector depletion layer of intrinsic (i-type) semiconductor to reduce greatly the collector capacitance and to increase the collector breakdown voltage. This structure will permit simultaneous achievement of high alpha cutoff frequency, low ohmic base resistance, low collector capacitance, and high collector breakdown voltage. Because of the high breakdow?i voltages and larger areas per unit capacitance, permissible power dissipations appear much larger than for other high frequency junction types. Theoretical calc ulations indicate that oscillations at frequencies as high as 3,000 mcps may be possible. Early exploratory models have verified the basic theory. Progress toward initial design objectives has been encouraging. In general, the observed performance has been consistent with the materials used and the structure achieved. The highest frequency of oscillation obtained to date is 95 mcps. Better performance is expected as technical control of materials and structures is improved. In the five years since the announcement of the junction transistor by Shockley, great steps have been made in extending its useful frequency range and its power-handling capacity. Recent developments, particularly those which have increased the frequency range,2, 12,13 have brought the performance of practical devices close to ultimate limits 517 518 T H E B E L L SYSTEM T E C H N I C A L J O U R N A L , MAY 1954 prescribed by structure and material.