Physical Electronics Dept.

***** Seminar *****

Dana Haran

(M.Sc. student under supervision of Prof. Yosi Shacham-Diamand,

School of EE, Dept. of Physical Electronics)

Study of P-i-N heterogenic diode made of Germanium on Silicon

We present here the results of a study of the electrical behavior of a P-i-N heterogenic diode made of Germanium-on-Silicon. This structure is commonly used to detect Infra-red wavelengths in high speed switching for photonic interconnects and other applications in the electro-optic communication field. The diode’s optical behavior is well studied and has been presented by numerous researchers; however, fewer have studied the physical phenomena origins behind its electrical characteristics. The research we present here tries to explain selected mechanisms as well as the effect of diode’s dimensions and materials on its performance. The diodes have been manufactured on standard Silicon wafer using CMOS technology. Evaluation and characterization of the diodes were done by simple methods such as current-voltage (I-V), capacitance-voltage (C-V) and reverse recovery time.

Synopsis of our research involves: study of surface traps effect on leakage current and forward current, attributed to passivation quality and explained by SRH model; evaluation of parameters like Ge deep traps energy level, surface traps density, depletion region width, threshold voltage and band-gap temperature dependence; minority carriers’ transit time. Theoretical models of the junction and its behavior were built and fit the experimental results. Energy levels model was conceived to enable the understanding of threshold voltage being close to 0V and the inversion of the built-in potential with temperature increase.

Results emphasized the crucial role of surface states recombination-generation mechanisms ruling diode’s current. Also, research discoveries included threshold voltage close to 0V, decrease of built-in potential with temperature due to bandgap narrowing, junction capacitance affected by the diode’s heterogenic structure, discovery of an upper limit to minority carriers’ transit time in the junction.

In conclusion, the research shaded light on the electrical aspects of this unique P-i-N heterogenic diode, enabling future development and improvement of its performance.