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For single crystal diamond (SCD) to gain practical use in technical applications including solid state electronics, thin (< $1 ~\mu \text{m}$), doped epitaxial SCD layers with very low (<1 nm) surface roughness are required. Conventional SCD chemical mechanical polishing (CMP) processes are insufficient to meet the requirements of such applications because the material removal rate (MRR) is often characterized inappropriately, and the material removal uniformity is seldom considered. In this study, chemical vapor deposition (CVD) growth of two lightly boron doped (p-) epilayers was performed on 3° misoriented (100) high pressure high temperature substrates of 4.5 x $4.5 mm^{2}$ area. A subsequent 8-hour oxidative CMP process utilizing potassium permanganate and a novel self-leveling holder design decreased the average surface roughness from 3.83 nm and 1.57 nm to 0.20 nm and 0.16 nm for the two samples, respectively. MRRs were determined by evaluating five circular wear monitor structures in each sample by atomic force microscopy before and after the CMP process. The average MRRs were found to be 38.6 nm/hr and 37.3 nm/hr for the two samples. The purpose of this study is to demonstrate a CMP process suitable for polishing thin SCD epilayers to meet the needs of solid-state electronics applications. [ABSTRACT FROM AUTHOR]

Diamond is a highly attractive ultrawide bandgap semiconductor for next-generation high-power switching devices and RF devices for its superior physical and electrical properties. However, the lack of effective n-type dopants in diamond has limited the material to only unipolar p-type device applications. Heterostructure bipolar devices that use better n-type semiconductors together with p-type diamond is an approach to get high performance devices. In this work, p–n–p AlGaAs/GaAs/diamond heterojunction bipolar transistors (HBTs) are proposed and fabricated using a grafting technique. The double-heterojunction is formed by transferring an AlGaAs(p-type)/GaAs(n-type) membrane onto single-crystalline p-type doped diamond with an electron affinity of 0.32 eV. The epitaxial AlGaAs/GaAs emitter-base p–n junction shows an ideality factor of 1.09 with an Ion/Ioff of 1.53 × 107 at ± 1.5 V. The grafted GaAs/diamond n–p junction shows an ideality factor of 3.67 with an Ion/Ioff of 3.74 × 1010 at ± 5.2 V. Due to the valence-band energy barrier of 0.3 eV between the GaAs base and the diamond collector, the measured current gain for the HBT is slightly below unity. Simulations show that by reducing the electron affinity value of the p-type diamond, the base-collector energy barrier height can be correspondingly reduced, and high current gain can be expected. [ABSTRACT FROM AUTHOR]