?iE!J PHOTOVOLTIC EFFECT IN SICONDUCTOR JUNCTIONS N/P

The application of mitiphotonic multistep absorption model to the 10,6 jim wave lertght laser inducedphotovoltaic potentials in silicon junctions is discussed. First observations in Germanium junctions are reported. 1. INTRODIXION Irradiation with 10,6 jim wave lenght radiation of N/P silicon junctions produces a induced photovoltaic potential as we reported in previous paper'. We also observed the effect in photoconductive mode in the same. silicon junctions2. A multistep multiphotonic process was proposed to exp.ian the main experimental results. In this comunication we discuse the multiphotonic model and report the first observation of the 10,6 jim induced photovoltage.n Germaniun junctions. 2. THEORET•EçAL APPROAcH As we pointed out in 1,2 muitiphotonic absorption takes place through a sequence of jumps by a photon in quariresonance with intermediate state placed within the energy gap. These intermediate states correspond to the known tayl of the density of states, which are found within the energy gap in highly doped semiconductors. The mechanism of the multiphotonic process may be described as follows. In the region N++ the photons are absorbed by free carriers in the conduction band leaving holes in states near the bottom of this band. The following step is the excite electrons in imurAty states inside the gap to the holes created in the prior step leaving the corresponding empty impurity states. After steps, the first holes appear in the top of the valence band. The entire process requires the absorption of a threshold energy during a fnite time as is experimentaly observed