Semiconductor Structures for 100 GHz Silicon IMPATT Diodes

Abstract

Single Drift, double drift and quasi Read double drift (QRDDR) silicon IMPATT diodes for CW operation are compared. It is shown that for high power generation efficient semiconductor structures have to be developed. A theoretical design study predicts an efficiency of 14.1 % for the QRDDR diode at 94 GHz. Experimental investigations are performed with diodes the active layers of which are grown by Si-MBE. The results confirm the predicted differences between the structures: The QRDDR diodes deliver the highest efficiency (up to 11 %) and the highest output power: 910 mW. I. BASIC PRINCIPLESMm-wave IMPATT diodes shall be optimized to deliver high output power. The CW-RF-power, which is obtained from two terminal devices, can be described by RF AT (1) RT Where n represents the external conversion efficiency, R the thermal resistance and t T the junction temperature rise. The maxi4um allowable junction temperature rise depends on the demanded life time of the diode and the employed contact materials. The thermal resistance mainly depends on the device area, contact layer, and heatsink design. Proceeding from a large-signal IMPATT diode impedance representation ([1],[2]) the internal efficiency of the diode is given from I * 1 -Cos e O D * F(m.u) (2) Idi with the transit angle e , the drift length 1 the depletion layer length 1 and a function F(m, u) which is deBendent on the modulation level m afQ the normalized RF-voltage u. If e =--3/4 is chosen, the value of the term (1-cos s )I e reaches his maximum with 0.71. For m = 0.4, as has been measured at X-band [3] the maximum of F(m, u) is 0.79 with u = 1.5. These assumptions simplify (2) to n= 17.8 *[D (3] dl From(3) it clearly follows that ID/Idl= 1 -AV'dI has to be maximized e.g. by confining the avalanche region length 1A'The authors are with the

A radiating monolithic integrated planar oscillator at 55 GHz

“…Fig. 1 shows the doping profile of the employed quasi read double drift IMPATT diode (QRDD) [3]. The design is slightly modified with respect to the introduction of a diffusion buffer in order to compensate for an outdiffusion of the boron-doped buried layer.…”