Ge diffusion at Ge/GaAs heterojunctions

Abstract

Interdiffusions at Ge/GaAs heterojunctions formed by the epitaxial deposition of Ge films on GaAs have been studied for temperatures ranging from 650–800 °C. The diffusion coefficients of Ge in GaAs have been found to be 1.6×10−5 exp(−2.06/kT) for Cr: and Si:doped GaAs. After the diffusion heat treatment, Ge was found to be p type and ohmic.

On the annealing mechanism of AuGe/Ni/Au ohmic contacts to a two-dimensional electron gas in GaAs/AlxGa1−xAs heterostructures

“…The temperature dependence alone governs the fitting result for E a , giving here 0.15 eV. This is on the low side for typical values for diffusion in GaAs materials (∼1 eV) [30][31][32] (for diffusion of Ge, Ni or Au in GaAs [30][31][32]), this fit yields C/C 0 very close to 1, i.e. completely saturated diffusion.…”

“…The results of this fitting are presented in figure 3(c), and v ocf as a function of temperature for these fitting parameters (E a = 0.6 eV and v 0 = 7.6 × 10 −5 m s −1 ) is plotted in figure 3(b). While it is a crude model, the fits are very reasonable, showing that the model is useful for predicting optimal annealing times (note that we use here the same activation energies and diffusion constants for Au and Ge, this is a reasonable approach since the values are found to be very close to each other [30][31][32]). Furthermore, the value for E a is a realistic number [30][31][32].…”

“…While it is a crude model, the fits are very reasonable, showing that the model is useful for predicting optimal annealing times (note that we use here the same activation energies and diffusion constants for Au and Ge, this is a reasonable approach since the values are found to be very close to each other [30][31][32]). Furthermore, the value for E a is a realistic number [30][31][32]. Our model also predicts that the minimum value of the resistance that can be achieved for optimally annealed contacts increases with increasing 2DEG depth.…”

Memory effect of Ge in III–V semiconductors

“…Hall measurements of the 2.5 mm thick GaAs layers show no difference in the overall doping level before and after the annealing. This may be explained by the small diffusion coefficient of Ge in GaAs [7] which leads to a shallow Ge doping profile near the surface. The effect on the overall carrier concentration in the 2.5 mm thick GaAs layer measured by Hall is negligible.…”

Effect of temperature on the mutual diffusion of Ge/GaAs and GaAs/Ge

“…Usually, this is the only parameter under control when realizing a diffused Ge junction by depositing a GaAs onto a Ge substrate. Element profile analysis with SIMS of GaAs/Ge diffusion has been published [9,15].…”