Abstract
Charge carrier trapping in diamond surface conduction field effect transistors (FETs) has been analyzed. For these devices two methods were used to obtain a negative electron affinity diamond surface; either plasma hydrogenation or annealing in an H2 environment. In both cases the Al2O3 gate dielectric can trap both electrons and holes in deep energy levels with emission timescales of seconds, while the diamond – Al2O3 interface traps exhibit much shorter time scales in the microsecond range. Capacitance-Voltage (CV) analysis indicates that these interface traps exhibit acceptor-like characteristics. Correlation with CV based free hole density measurements indicates that the conductance based interface trap analysis provides a method to quantify surface characteristics that lead to surface conduction in hydrogenated diamond where atmospheric adsorbates provide the acceptor states for transfer doping of the surface.
Highlights
Group III-nitride electronics have demonstrated a substantial scale up of power and frequency performance over that of GaAs and other high frequency material systems
In this work we describe the transient performance of our transfer doped diamond field effect transistors (FETs)
Effective mobility was measured by calculating the charge under the gate utilizing a CV measurement. Both hydrogenation processes led to FETs with typical output characteristics as shown in figure 1(a) for the wafer hydrogenated by annealing in an H2 environment
Summary
Group III-nitride electronics have demonstrated a substantial scale up of power and frequency performance over that of GaAs and other high frequency material systems As these devices are tasked in challenging high power RF applications, we are seeing limitations due to heat generation and removal. [2] Given the large ionization energies of bulk dopants in diamond, we are instead considering surface conduction devices These are formed using a hydrogenated diamond surface which exhibits a negative electron affinity that aligns the valence band with acceptor states in an adjacent surface layer material. The other was exposed to a hydrogen plasma for 60 minutes during which the wafer temperature was 800 °C In these FETs atmospheric adsorbates on the hydrogenated diamond surface act as transfer dopants. Effective mobility was measured by calculating the charge under the gate utilizing a CV measurement
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