Boron‐Doped Single‐Crystal Diamond Growth on Heteroepitaxial Diamond Substrate Using Microwave Plasma Chemical Vapor Deposition

Abstract

Boron‐doped diamond layers are grown on freestanding heteroepitaxial diamond substrates by microwave plasma chemical vapor deposition (MPCVD) to verify the high potential of large‐size heteroepitaxial diamond as an ultimate semiconductor material. Due to the high crystallinity and atomically flat surface morphology of the substrate, the MPCVD‐grown boron‐doped diamond layer exhibit excellent surface properties and crystallinity, as measured by X‐ray diffraction and atomic force microscopy. The temperature‐dependent Hall effect measurements are conducted at temperature ranges between 300–800 K with cloverleaf‐shaped van der Pauw geometry. The hole concentration of boron‐doped diamond samples is between 1.1 × 1015 and 5 × 1019 cm−3 at room temperature, and the resistivity is controlled between 10−1 and 20 Ω cm by changing boron to carbon ratio. A specific contact resistance as low as 1.41 × 10−4 Ω cm2 is obtained via annealing at 500 °C. The activation energy of the boron‐doped diamond layers is reduced from 0.35 to 0.12 eV as the amount of boron dopant increases, which is attributed to the formation of impurity band. Finally, the change in the carrier mobility of boron‐doped heteroepitaxial diamond is discussed based on the scattering mechanism.

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“…The p-type diamond (001) sample was a CVD-grown, B-doped single crystal, with a boron concentration of around 10 15 cm À3 (Element Six Ltd.). 23 The diamond (6 Â 8 Â 1 mm 3 ) was scaife-polished and oxidised using 10 mL of sulphuric acid and 0.5 g potassium nitrate, followed by cleaning in water and organic solvents and drying in N 2 gas before mounting in the spectrometer.…”

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“…Heteroepitaxial diamond substrates were explored for B-doping as well. Recently, different groups have investigated Ir [ 175 ] and other heteroepitaxial diamond substrates [ 176 , 177 ] to grow B-doped epilayers and overlayers (p+ and p−) of different thicknesses with B concentrations ranging from (10 15 –10 20 cm −3 ). They have also reported on the Hall mobility of 390 cm 2 /Vs for a B concentration of 1 × 10 18 cm −3 in a diamond epilayer [ 176 ].…”

“…Recently, different groups have investigated Ir [ 175 ] and other heteroepitaxial diamond substrates [ 176 , 177 ] to grow B-doped epilayers and overlayers (p+ and p−) of different thicknesses with B concentrations ranging from (10 15 –10 20 cm −3 ). They have also reported on the Hall mobility of 390 cm 2 /Vs for a B concentration of 1 × 10 18 cm −3 in a diamond epilayer [ 176 ]. However, boron-doped p-type diamonds have demonstrated Hall mobility as high as 2200 cm 2 /Vs at room temperature [ 178 ].…”

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“…Hole concentrations were tuned from 1.1 × 10 15 to 5 × 10 19 cm −3 at room temperature by increasing the boron concentration. [ 179 ] The doped epilayer with a boron concentration of 1 × 10 18 atoms per cm 3 shows a mobility of 390 cm 2 V −1 s −1 according to Hall measurements. Such a value is intermediate compared with similar doped epilayer grown on homoepitaxial diamond ( Figure ).…”

“…Hole mobility measured at 300 K versus the boron concentration for heteroepitaxial diamond compared to homoepitaxial diamond. Reproduced with permission [179]. Copyright 2020, Wiley-VCH.…”