Time-dependent hydrogen annealing of Mg-doped GaN Ustun R. Sunay J. Dashdorj M. E. Zvanut This work is funded the National Science Foundation, Grant No. DMR

Outline Motivation –What can GaN do for us? Background –What do we need to know about Mg-doped GaN? –Explain electron paramagnetic resonance (EPR) Experiment –What are the parameters of our experiment? Results –EPR spectra Summary - Alloying GaN with aluminum changes the kinematics of hydrogen passivation.

Why Care About GaN? Why Care About GaN? Other list of Applications High frequency devices High electron mobility transistors- used in radar imaging, radio astronomy, etc….

Background Mg doped GaN is a p-type semiconductor Mg + Mg concentration is ~10 19 cm -3 GaN density is ~10 22 cm -3 Main Point Study hydrogen interaction in p-type GaN and its alloys.

H-H Surface of sample Mg-N H + + GaN Film H 2 ”rich” atmosphere e-e- This hydrogen interaction with Mg+ makes the semiconductor less effective

EPR ΔE = g μ B B o Bruker Analytische Messtechnik ESP300 User’s Manual EPR Primer page 2.1 Δ E=h f

Experimental Details GaN was grown on sapphire substrate using MOCVD. Concentration of Mg ~4x10 19 cm -3 Al x Ga 1-x N: x ranging from EPR at 4 K : Microwave frequency ~ 9.4 GHz Sapphire substrate AlN AlGaN AlN Al x Ga 1-x N:Mg Sample 2.5 cm1 μm

FURNACE DETAILS Isochronal annealing steps ranged from 5 min- 360 min at temperatures ranging from 300 o C to 750 o C in forming gas(7%H 2 :93%N 2 )

Mg signal increases in intensity at low temperature anneals for 0% Al

At high Al %, the process of passivating has slowed down.

Summary After annealing from 300 o C o C the Mg signal intensity in 0% Al increases Preliminary data suggest that at 700 o C, high % Al has a slower passivation rate The Mg signal passivates for all samples at 700 o C after being annealed for ~6 h Alloying GaN with aluminum changes the kinematics of hydrogen passivation.