Ohmic contacts and schottky barriers to n-GaN

Tunneling coefficient for GaN Schottky barrier diodes

“…where C T is the tunneling coefficient, A is the Richardson constant (24 A cm À2 K À2 , [16]), T is the temperature, k is Boltzmann's constant, / BN is the Schottky barrier height, D/ BN is the reduction of the barrier height due to the image force lowering phenomenon. The Schottky barrier lowering is given by:…”

Thermally stable Ge/Cu/Ti ohmic contacts to n-type GaN

“…Traditionally, contact schemes with titanium metal as the first layer have been most widely used. [8][9][10][11]15,22 Ti is selected as the first contact layer to n-type GaN because its work function, 4.33 eV, is close to that of n-GaN (electron affinity 5 4.1 eV). Ohmic behavior of a GaN/Ti system has been attributed to the out-diffusion of nitrogen from the GaN into the Ti, creating N vacancies, which act as donors at the GaN surface.…”

“…Ohmic behavior of a GaN/Ti system has been attributed to the out-diffusion of nitrogen from the GaN into the Ti, creating N vacancies, which act as donors at the GaN surface. 8,10,11,22 The introduction of excess donors at the metal/n-GaN interface causes carrier tunneling through the thin metal/ semiconductor barrier, which results in an ohmic behavior to the contact system. Ti is also known to reduce native oxide on the GaN surface, thus promoting more intimate metal-to-GaN contact.…”

Metal contacts to n-type GaN

“…Much work has been done already to discover the nature of metal/GaN Schottky contacts. [1][2][3][4][5][6][7][8][9][10][11][12] However, most of these works describe the Schottky diode characteristics for only one or two metals, and none encompass more than four metals. Comparisons between works can be misleading due to great differences in the measurement techniques, the GaN epilayer quality, carrier concentration, and surface preparation before metal deposition.…”