Formation of an n-GaAs/n-GaAs regrowth interface without carrier depletion using electron cyclotron resonance hydrogen plasma

We report on the formation of a GaAs MBE regrowth interface without carrier depletion and contaminants using electron cyclotron resonance (ECR) hydrogen plasma. The mechanism for removing GaAs surface-contaminants such as Si, O, and C has been investigated to realize a contaminant-free regrowth-interface. Secondary ion mass spectroscopy (SIMS) analysis shows that Si and O contaminants result not only from adsorption when exposed to air prior to regrowth but also from the sputtering of the quartz liner in the ECR chamber during plasma treatment. These can be reduced to a level below the SIMS detection limit by lowering the hydrogen pressure to below 10^-3 Torr, because sputtering can be suppressed. SIMS also reveals that the C contaminant can be removed at substrate temperatures above 400°C to a level below the SIMS detection limit. This was verified through thermal desorption spectroscopy (TDS) analysis. This is because the C contaminant is removed through transformation into CH₃ at substrate temperatures above 400°C. Furthermore, reflection high-energy electron diffraction (RHEED) observation, atomic force microscopy (AFM) and capacitance-voltage (C-V) measurements indicate that both structural and electrical damage induced by ECR plasma is completely eliminated at 500°C. Based on these methods, we are able to produce an undamaged and contaminant-free MBE regrowth interface on n-GaAs/n-GaAs for the first time.