The current-voltage (I-V) characteristics of Au/n-GaAs contacts prepared with photolithography technique have been measured in the temperature range of 80-320K. The ideality factor and barrier height (BH) values have remained almost unchanged between 1.04 and 1.10 and at a value of about 0.79 eV at temperatures above 200K, respectively. Therefore, the ideality factor values near unity say that the experimental I-V data are almost independent of the sample temperature, that is, contacts have shown excellent Schottky diode behavior above 200K. An abnormal decrease in the experimental BH Phi(b) and an increase in the ideality factor with a decrease in temperature have been observed below 200 K. This behavior has been attributed to the barrier inhomogeneity by assuming a Gaussian distribution of nanometer-sized patches with low BH at the metal-semiconductor interface. The barrier inhomogeneity assumption is also confirmed by the linear relationship between the BH and the ideality factor. According to Tung's barrier inhomogeneity model, it has been seen that the value of sigma(T) = 7.41 x 10(-5) cm(2/3) V-1/3 from ideality factor versus (kT)(-1) curve is in close agreement with sigma(T) = 7.95 x 10(-5) cm(2/3) V-1/3 value from the Phi(eff) versus (2kT)(-1) curve in the range of 80-200K. The modified Richardson ln(J(0)/T-2)-(q sigma(T))(2)(V-b/eta) (2/3)/[2(kT)(2)] versus(kT)(-1) plot, from Tung's Model, has given a Richardson constant value of 8.47 A cm(-2) K-2 which is in very close agreement with the known value of 8.16 A cm(-2) K-2 for n-type GaAs; considering the effective patch area which is significantly lower than the entiregeometric area of the Schottky contact, in temperature range of 80-200K. Thus, it has been concluded that the use of Tung's lateral inhomogeneity model is more appropriate to interpret the temperature-dependent I-V characteristics in the Schottky contacts. (C) 2013 Elsevier B.V. All rights reserved.
The current–voltage(I–V) characteristicsofAu/n-GaAscontactspreparedwithphotolithography
techniquehavebeenmeasuredinthetemperaturerangeof80–320K.Theidealityfactorandbarrier
height (BH)valueshaveremainedalmostunchangedbetween1.04and1.10andatavalueofabout
0.79 eVattemperaturesabove200K,respectively.Therefore,theidealityfactorvaluesnearunitysay
that theexperimental I–V data arealmostindependentofthesampletemperature,thatis,contacts
have shownexcellentSchottkydiodebehaviorabove200K.Anabnormaldecreaseintheexperimental
BH Fb and anincreaseintheidealityfactorwithadecreaseintemperaturehavebeenobservedbelow
200 K.ThisbehaviorhasbeenattributedtothebarrierinhomogeneitybyassumingaGaussian
distributionofnanometer-sizedpatcheswithlowBHatthemetal-semiconductorinterface.Thebarrier
inhomogeneityassumptionisalsoconfirmedbythelinearrelationshipbetweentheBHandtheideality
factor.AccordingtoTung’sbarrierinhomogeneitymodel,ithasbeenseenthatthevalueof
sT¼7.41105 cm2/3 V1/3from idealityfactorversus(kT)1 curve isincloseagreementwith
sT¼7.95105 cm2/3 V1/3 value fromthe Feff versus(2kT)1 curve intherangeof80–200K.The
modifiedRichardsonln(J0/T2)(qsT)2(Vb/Z)2/3/[2(kT)2] versus(kT)1 plot, fromTung’sModel,hasgiven
a Richardsonconstantvalueof8.47Acm2 K2which isinverycloseagreementwiththeknownvalue
of 8.16Acm2 K2 for n-type GaAs;consideringtheeffectivepatchareawhichissignificantlylower
than theentiregeometricareaoftheSchottkycontact,intemperaturerangeof80–200K.Thus,ithas
been concludedthattheuseofTung’slateralinhomogeneitymodelismoreappropriatetointerpretthe
temperature-dependent I–V characteristicsintheSchottkycontacts.