Analysis of semiconductors with field-dependent mobility
Using the time domain analysis of Lagrangian approach, the small-signal behavior of a semiconductor with field-dependent mobility under various contact conditions is analyzed. A generalized closed form solution for an impulse current response is derived when the carrier velocity characteristic is expressed by a piecewise linear function. This result gives an accurate description of the transient performance of the device and can provide good insight into device operation. Numerical examples are given for a negative differential mobility GaAs crystal, considering the conditions under which negative resistances occur. A generalized small-signal impedance of the semiconductor is given, from which previous results reported for particular devices can be obtained as special cases.
Stability criterion for Gunn diodes with injection-limiting cathodes
According to McCumber [1] a Gunn diode with an ohmic cathode (i.e., "differential cathode conductivity" \sigma_{c} = \delta ) is stable in a constant-voltage circuit if n_{0}L \le (n_{0}L)_{crit} \equiv 2.7 \times 10^{11} cm-2where n_{0}L is the doping-length product. We show that the same stability criterion applies to Gunn diodes with an injection-limiting cathode (\sigma_{c} \rightarrow 0) , if (n_{0}L)_{crit} is allowed to be a function of \sigma_{c}L . The value of (n_{0}L)_{crit} increases by 30 percent if (\sigma_{c}L) varies from infinity (ohmic cathode) to zero (injection-limiting cathode). If a cathode with negative differential conductivity is realizable, it may be possible to extend the (n_{0}L) region of stable operation of Gunn diodes drastically.
Simulating the Illuminance and Efficiency of the LEDs Used in General Household Lighting
Abstract The advantage of the LEDs illumination in general household lighting was proposed. High efficiency white LED as the light source was provided the energy saving illumination of the general household lightings. Different spaces in general household with different standards of average illuminance were designed and simulated by LightTools and DIALux software. The power consumptions and efficiency of traditional illuminated light sources and LED light source in lighting the household environment were analyzed and compared with each other at the same standard of average illuminance. Finally, it provided the advantage of using white LEDs in different spaces of the general household lighting.