In the contact rectifier described, the cat whisker has been solidly welded to a germanium surface. The welding process has brought about several extraordinary properties not found in the usual point rectifier: (1) Mechanical stability is achieved without the use of a compound to fill the cartridge. Protection against moisture is gained through the use of a glass‐metal seal. (2) The forward dynamic resistance of the microwave unit at 0.5 volt is exceptionally low (2 to 4 ohms), and the back resistance at 0.5 volt is high (0.01 to 1.0 megohm). These values of resistance are accompanied by a low contact capacity at zero bias (below 0.2 μμf). (3) The forward d.c. characteristic follows the law, IF=I0 exp (αVF) over more than three decades of current. (4) The low forward resistance is responsible in part for conversion gain when the crystals are mismatched to microwave radiation at the r‐f terminals. (5) Specially welded crystals used as microwave harmonic generators have yielded more than twenty times the harmonic (4‐mm wave‐length) power output of standard silicon crystals.

This work was done in part under Contract No. OEMsr‐1377 between the General Electric Company and the Office of Scientific Research and Development and under subcontract with the Massachusetts Institute of Technology, Prime contract OEMsr‐262. The OSRD assumes no responsibility for the statements contained herein.
This paper is a condensation of material presented by the author to the University of California at Los Angeles in partial fulfillment of the requirements for the degree of Doctor of Philosophy in Physics.
N. F. Mott and R. W. Gurney, Electronic Processes in Ionic Crystals (Clarendon Press, Oxford, 1940).
F. Seitz, The Modern Theory of Solids (McGraw‐Hill Book Company, Inc., New York, 1940).
This treatment has been described in reports having only limited distribution. A more detailed discussion will be found in a forthcoming book by H. C. Torrey and C. A. Whitmer of the M.I.T. Radiation Laboratory, Crystal Rectifiers (McGraw‐Hill Book Company, Inc., New York, 1946).
H. T.
, “
Noise figures of radio receivers
Proc. I.R.E.
S. Roberts, 1N23 Noise Measuring Set Type 7438, Radiation Laboratory Report M‐190 (Dec. 21, 1944).
E. C.
, “
Germanium crystal diodes
In measuring VL in the region of low or negative i‐f conductance, it is important either that the percent modulation be small enough or that the load line be steep enough to prevent distortion of the wave due to a large voltage swing at the i‐f terminals. Six‐percent modulation and a load of 100 ohms were found to be satisfactory.
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