Computation of Heterojunction Parameters at Low Temperatures in Heterojunctions Comprised of n-Type _-FeSi2 Thin Films and p-Type Si(111) Substrates Grown by Radio Frequency Magnetron Sputtering

Abstract

In this study, n-type β -FeSi 2 /p-type Si heterojunctions, inside which n-type β -FeSi 2 films were epitaxially grown on p-type Si(111) substrates, were created using radio frequency magnetron sputtering at a substrate temperature of 560°C and Ar pressure of <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" id="M1"><mml:mn fontstyle="italic">2.66</mml:mn><mml:mo>×</mml:mo><mml:msup><mml:mrow><mml:mn fontstyle="italic">10</mml:mn></mml:mrow><mml:mrow><mml:mo>-</mml:mo><mml:mn fontstyle="italic">1</mml:mn></mml:mrow></mml:msup></mml:math> Pa. The heterojunctions were measured for forward and reverse dark current density-voltage curves as a function of temperature ranging from 300 down to 20 K for computation of heterojunction parameters using the thermionic emission (TE) theory and Cheung’s and Norde’s methods. Computation using the TE theory showed that the values of ideality factor (<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" id="M2"><mml:mrow><mml:mi>n</mml:mi></mml:mrow></mml:math>) were 1.71 at 300 K and 16.83 at 20 K, while the barrier height (<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" id="M3"><mml:mrow><mml:msub><mml:mrow><mml:mi>ϕ</mml:mi></mml:mrow><mml:mrow><mml:mi>b</mml:mi></mml:mrow></mml:msub></mml:mrow></mml:math>) values were 0.59 eV at 300 K and 0.06 eV at 20 K. Both of the <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" id="M4"><mml:mrow><mml:mi>n</mml:mi></mml:mrow></mml:math> and <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" id="M5"><mml:mrow><mml:msub><mml:mrow><mml:mi>ϕ</mml:mi></mml:mrow><mml:mrow><mml:mi>b</mml:mi></mml:mrow></mml:msub></mml:mrow></mml:math> values computed using the TE theory were in agreement with those computed using Cheung’s and Norde’s methods. The values of series resistance (<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" id="M6"><mml:mrow><mml:msub><mml:mrow><mml:mi>R</mml:mi></mml:mrow><mml:mrow><mml:mi>s</mml:mi></mml:mrow></mml:msub></mml:mrow></mml:math>) computed at 300 K and 20 K by Norde’s method were 10.93 Ω and 0.15 MΩ, respectively, which agreed with the <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" id="M7"><mml:mrow><mml:msub><mml:mrow><mml:mi>R</mml:mi></mml:mrow><mml:mrow><mml:mi>s</mml:mi></mml:mrow></mml:msub></mml:mrow></mml:math> values found through computation by Cheung’s method. The dramatic increment of <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" id="M8"><mml:mrow><mml:msub><mml:mrow><mml:mi>R</mml:mi></mml:mrow><mml:mrow><mml:mi>s</mml:mi></mml:mrow></mml:msub></mml:mrow></mml:math> value at low temperatures was likely attributable to the increment of <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" id="M9"><mml:mrow><mml:mi>n</mml:mi></mml:mrow></mml:math> value at low temperatures.