Presentation Details
| Mechanism of ohmic contact resulting from heavily doped p-n junction: A novel explanation in terms of impurity-photovoltaic-effect due to infrared self-emission at room-temperature Jianming Li. Institute of Semiconductors, Chinese Academy of Sciences, Beijing, China |
Abstract
The ohmic contact connection of two p-n junctions is used e.g. in tandem solar cells. In textbooks, ohmic contact is explained by quantum-mechanical tunneling based on electron-wavefunction. Tunneling is an example of wave-particle duality. In this study, an attempt is made to explain ohmic contact in particle description. As is well known, any object at room-temperature emits infrared (IR) photons due to blackbody radiation. The process of heavy doping can cause a lot of defects, e.g. vacancies and interstitials. The self-absorption of the IR emission could be achieved through sub-band-gap excitations due to defects, creating carriers. In a heavily doped p-n junction diode, some of the IR-generated carriers diffuse into the junction which has a built-in field in a depletion layer. The built-in field then sweeps out the carriers, producing IR photocurrent. The reverse current of the p-n junction is regarded as the IR photocurrent according to the precedent where impurity-photovoltaic-effect is used to explain circuit devices (arXiv:2510.18226). Also, reverse voltage increases depletion layer width, but the carrier diffusion length out of the depletion layer remains unchanged, and more IR-generated carriers created in and near the depletion layer can contribute to the IR current. In addition, heavy doping causes not only a great many IR-generated carriers but also avalanche effect at lower voltage. As a result, total reverse current dramatically increases with voltage and a p-n junction becomes an ohmic contact. Not only quantum mechanics, but also this photovoltaic mechanism in particle description can explain ohmic contact. Considering wave-particle duality, the combination of quantum-mechanical and photovoltaic mechanisms is suggested to explain ohmic contact. Each mechanism plays a big or small role in the explanation.
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