Characteristics and parameter extraction for NiGe/n-type Ge Schottky diode with variable annealing temperatures

Current transport mechanism in Ni-germanide/n-type GeSchottky diodes is investigated using current--voltagecharacterisation technique with annealing temperatures from 300~duto 500~du. Based on the current transport model, a simple method toextract parameters of the NiGe/Ge diode is presented by using the$I$--$V$ characteristics. Parameters of NiGe/n-type Ge Schottkydiodes fabricated for testing in this paper are as follows: theideality factor $n$, the series resistance $R_{rm s}$, thezero-field barrier height $phi _{rm b0}$, the interface statedensity $D_{rm it}$, and the interfacial layer capacitance $C_{rmi}$. It is found that the ideality factor $n$ of the diode increaseswith the increase of annealing temperature. As the temperatureincreases, the interface defects from the sputtering damage and thepenetration of metallic states into the Ge energy gap arepassivated, thus improving the junction quality. However, theundesirable crystallisations of Ni-germanide are observed togetherwith NiGe at a temperature higher than 400~du. Depositing a verythin ($sim $1~nm) heavily Ge-doped $n^{+}$ Ge intermediate layercan improve the NiGe film morphology significantly.