Dark current and noise in In/Zn/p-InAs and In/n-InAs

In review articles [1,2] the methods of preparation as well as basic properties of ohmic contacts metal-semiconductors A 3 B 5 are generalized. Chemical treatment of n-InAs result in pinning of a Fermi level by surface states in a conduction band [2,3]. Thus, the near-surface area is enriched by majority carriers. The deposition of a metal on n-InAs with tunnel-transparent native oxide results in structures with an antiblocking contact. In chemically treated samples of p-InAs the pinning of a Fermi level in a conduction band causes a strong band bending of an order of the gap's width of InAs [3,4] and formation of an inversion layer. The deposition of a metal on p-InAs transforms this structure into an imperfect Schotky diode, the height of a potential barrier in which does not depend on a work function of a metal. For transformation of rectifying structure metal-p-InAs into non-rectifying with linear current-voltage characteristics the formation of highly doped near-surface p+-InAs layer is used by means of epitaxial growth [5,6], or thermal diffusion of an acceptor impurity, such as Zn with its high solubility in InAs [2,4,7]. The availability p+-InAs layer results in tunnel current mechanism through a depletion region, linear current-voltage characteristic and decrease of a contact resistance. The contact material to p+-type layer in the case of its epitaxial growth is Ti in the structure Au/Ti [5] or Be in the structure Au/Be [6]. The necessity of thermal treatment of such contacts was not indicated. In the case of diffusive formation of p+-area, as a rule, the alloys on the basis of indium In-Zn [4] or In-Ni Zn [7] are deposited by thermal evaporation followed by the thermal treatment. However, the temperature of the treatment was unknown in these articles. It should be pointed out that imperfect contacts can influence the magnitude of a noise and its frequency dependence and, therefore, the values of the detectivity of InAs photodiodes. In accordance with the above-stated, the purpose of the present work is to study influence of thermal treatment of In/Zn/p-InAs, In/n-InAs structures on their electrical and noise performances and finding-out capability of formation of low-noise ohmic contacts top- and n-InAs materials.