Influence of hydrogen treatment and annealing processes upon the Schottky barrier height of Au/n-GaAs and Ti/n-GaAs diodes

Abstract

After annealing in a H 2 atmosphere at different temperatures, 100 -oriented n-GaAs substrates were metallized with Au and Ti layers of different thicknesses to form Au/n-GaAs and Ti/n-GaAs Schottky diodes. The Schottky barrier height (SBH) variation and its dependence on subsequent N 2 annealing for these Schottky diodes have been studied by different measurement techniques (I-V, C-V and BEEM) to obtain reliable values. These methods show that pre-metallization annealing leads to a less homogeneous metal semiconductor (MS) interface. In case of thick Au layers the effective barrier height is reduced as soon as the H 2 annealing temperature reaches 300 • C. However, GaAs samples covered with thin Au layers or Ti layers do not exhibit such a barrier height reduction. The lower value in the case of thick Au layers is attributed to H + groups, present at the interface due to the annealing in H 2 atmosphere, forming interfacial dipoles with Au, leading to an inhomogeneous barrier and a decrease of the effective barrier height. It seems that these dipoles disappear again in the case of thin Au layers or are not formed with Ti. Post-metallization N 2 annealing at higher temperatures lowers the barrier height for all samples. The resulting barrier inhomogeneities are explained and analysed using the bond polarization theory of Tung ( 2001

Electrical characteristics of the hydrogen pre-annealed Au/n-GaAs Schottky barrier diodes as a function of temperature

“…giving rise to an extra current such that the overall characteristics still remain consistent with the TE process [14]. In 2005, Forment et al [2] have reported using Tung's pinch-off theory that the standard deviation s of the patch parameter g, and consequently of the patch radius R 0 and of the barrier height reduction D, are larger for the diode pre-annealed in H 2 atmosphere. Also according to them [2], another important result is the fact that the patch density r p is much smaller for diodes with H 2 pre-anneal.…”

“…In 2005, Forment et al [2] have reported using Tung's pinch-off theory that the standard deviation s of the patch parameter g, and consequently of the patch radius R 0 and of the barrier height reduction D, are larger for the diode pre-annealed in H 2 atmosphere. Also according to them [2], another important result is the fact that the patch density r p is much smaller for diodes with H 2 pre-anneal. They have attributed to that the total current after H 2 pre-annealing is dominated by a few large patches, while in the absence of this pre-metallization treatment a larger number of small patches are responsible for the current and, in agreement with the fact that according to thermionic theory the main part of the current will flow through patches with a low SBH Also, as shown in Fig.…”

“…It is well known that interface properties of the Schottky contacts have a dominant influence on the device performance, reliability and stability [2][3][4][5][6][7][8]. It can be stated more clearly that the surface-preparation methods serve advantages because Schottky metallization generally causes an interfacial modification.…”

“…In the past few decades, some scientists have reported noteworthy works for passivating surface/ interface defects of semiconductors like GaAs, Si, InP, etc. [1][2][3][18][19][20][21][22][23][24]. For instance, Kang and Park [1] applied to surface-cleaned (etched) GaAs the sulfidation and subsequent hydrogenation treatment to investigate the passivation mechanism and found that these sulfidation and subsequent hydrogenation processes caused no damage to the GaAs substrate.…”

“…They reported that the method proposed by them could be used for evaluating the perfection of the Pd/InP Schottky interface. Also, Forment et al [2] metallized the n-GaAs substrate pre-annealed in a H 2 atmosphere with Au and Ti layers of different thicknesses. They proposed that the resulting barrier inhomogeneities could be explained and analyzed using the bond polarization theory of Tung. The current transport across a Schottky junction is of interest to material physicists and device physicists.…”