Hi, need to submit a 3500 words essay on the topic Contacts to ZnO (zinc oxide).Furthermore, as ZnO films and crystals may be interfaced with a variety of metals to form schottky and ohmic contacts. Z

Hi, need to submit a 3500 words essay on the topic Contacts to ZnO (zinc oxide).

Furthermore, as ZnO films and crystals may be interfaced with a variety of metals to form schottky and ohmic contacts. ZnO contacts have the capability of replacing conventional or time tested materials that have been used including the AlInGaN system and so, ZnO contacts may pave way for more reliable and less costly appliances.

ZnO has a hexagonal or wurtzite crystal structure. The wurtzite structure is formed with the Zn atoms being tetrahedrally coordinated with four O atoms. This allows the Zn d shell electrons to hybridize with the p shell of O. ZnO has a density of 5.606 g/cm3, melting point of 1975°C and exciton binding energy of 60mEV. The compound is a direct band gap semi conductor that has Eg=3.2eV. ZnO can be molded to produce desired electrical properties by divalent subsititution on the cation site. ZnO supports both n-type and p-type doping. The presence of Zn interstitials, O vacancies and hydrogen .The intrinsic level defects that cause n-type doping are 0.01-0.05eV below the conduction band. The material possesses an intrinsic direct band gap, a strong exciton state and gap states due to the presence of point defects. A study of the optical properties of ZnO by use of photoluminesence, photoconductivity and absorption confirms the presence of point defects[10]..

ZnO is a wide gap semi conductor. Wide gap semi conductors are known to be more susceptible to n type doping. such as n-type doping through of ZnO through addition of excess Zn, Aluminum or Gallium. In this instance ZnO can be easily doped to form n-type material rather than p-type material. The reason behind the difficulty in doping ZnO to form p-type material can be linked to a number of reasons. In some cases, the inate point defects within the material compensate for the additional impurity by forming deep level traps. In other instances strong lattice relaxations push the dopant energy level deeper into the