Abstracf-A microwave detector based on the thermoelectric effect of warm carriers in bulk semiconductors is described. An analysis of device performance is presented, which is based on the assumption of a Maxwell-Boltzmann distribution for the heated carriers. The performance of a number of experimental devices at millimeter and centimeter wavelengths is shown to be in good agreement with analytic predictions. Outstanding characteristics of these devices are high detection sensitivity, high bum-out power, and high electrical stability over long periods of use.

No abstract

A theory is developed for the voltage arising from a gradient in a high electric field, i.e., a field sufficient to change the average energy of the carriers, and applied to calculations for the warm-carrier region in a semiconductor. For a situation in which there is a region of constant field E next to a region, consisting of the same material, in which the field decreases to zero, it is found that, for E in the warm-electron range, the field-gradient voltage is proportional to E2. This dependence is found experimentally for both n and p germanium at room temperature. Because a region of inhomogeneous material at a contact also makes some contribution to the measured voltage, it is not possible to make a quantitative comparison between experiment and theory. The contribution of the contact is found to depend on the nature of the transition region between semiconductor and metal and, in the hot-electron region, upon the magnitude of the electric field.

The effect on the conductivity of germanium and silicon samples of 2.85-kMc electric fields up to peak values of 10 000 v/cm was measured. These measurements differ from earlier ones in that: (1) the microwave field was in the form of progressive rather than standing waves, which made possible more accurate determination of the field strength in the sample, and (2) to determine whether any frequency effects occur at 2.85-kMc conductivity was measured at high dc fields on the same samples. From the average conductivity under microwave excitation the instantaneous conductivity was calculated and found to agree, within experimental error, with the dc conductivity, indicating that the conductivity can still follow the 2.85-kMc field at least up to peak fields of 10 000 v/cm.

ZnO thin-film loading of YZ-LiNbO3 is used to suppress all the harmonic generations of surface acoustic waves (SAW’s) in the substrate. An optical probing technique is used to measure the intensity variations of the harmonics as a function of acoustic power. Only the first-order diffracted light intensity is observed owing to the suppression of higher harmonic generations of SAW’s. This linearization of the first-order diffracted light intensity versus acoustic power is found to be independent of the interaction length (up to 5 mm) and the acoustic power (up to 4.3 W). The attenuation of SAW’s on YZ-LiNbO3 with a 2-μm ZnO layer was measured to be about 5 dB/cm at 325 MHz.