A synthetic single crystal diamond that includes nitrogen atoms at a concentration of 50 ppm to 1000 ppm, wherein the synthetic single crystal diamond contains an aggregate composed of one vacancy and two substitutional nitrogen atoms present adjacent to the vacancy, a ratio b/a of a length b of a longer diagonal line of a second Knoop indentation to a length a of a longer diagonal line of a first Knoop indentation is 0.90 or less on the synthetic single crystal diamond, the first Knoop indentation is an indentation formed on a surface of the synthetic single crystal diamond in a state where a Knoop indenter is pressed in a <110> direction of a {110} plane in accordance with JIS Z 2251:2009, and the second Knoop indentation is a Knoop indentation remaining on the surface of the synthetic single crystal diamond after the test load is released.

A synthetic single crystal diamond that includes nitrogen atoms at a concentration of 50 ppm to 1000 ppm, wherein the synthetic single crystal diamond contains an aggregate composed of one vacancy and two substitutional nitrogen atoms present adjacent to the vacancy, a ratio b/a of a length b of a longer diagonal line of a second Knoop indentation to a length a of a longer diagonal line of a first Knoop indentation is 0.90 or less on the synthetic single crystal diamond, the first Knoop indentation is an indentation formed on a surface of the synthetic single crystal diamond in a state where a Knoop indenter is pressed in a <110> direction of a {110} plane in accordance with JIS Z 2251:2009, and the second Knoop indentation is a Knoop indentation remaining on the surface of the synthetic single crystal diamond after the test load is released.

A synthetic single crystal diamond that includes nitrogen atoms at a concentration of 50 ppm or more and 1200 ppm or less in terms of number of atoms, wherein an infrared absorption spectrum of the synthetic single crystal diamond has an absorption signal within a wavenumber range of 1460 cm.sup.?1 or more and 1470 cm.sup.?1 or less.

A synthetic single crystal diamond that includes nitrogen atoms at a concentration of 50 ppm or more and 1200 ppm or less in terms of number of atoms, wherein an infrared absorption spectrum of the synthetic single crystal diamond has an absorption signal within a wavenumber range of 1460 cm.sup.?1 or more and 1470 cm.sup.?1 or less.

It is produced a crystal of a nitride of a group 13 element in a melt including the group 13 element and a flux including at least an alkali metal under atmosphere comprising a nitrogen-containing gas. An amount of carbon is made 0.005 to 0.018 atomic percent, provided that 100 atomic percent is assigned to a total amount of said flux, said group 13 element and carbon in said melt.

It is produced a crystal of a nitride of a group 13 element in a melt including the group 13 element and a flux including at least an alkali metal under atmosphere comprising a nitrogen-containing gas. An amount of carbon is made 0.005 to 0.018 atomic percent, provided that 100 atomic percent is assigned to a total amount of said flux, said group 13 element and carbon in said melt.

The purpose of diffusion assisted crystal hydrothermal growth is to facilitate a greatly increased crystal growth rate that would save time that is precious in such a material and manpower costly process. The assisted crystal growth itself requires the utilization of a piezoelectric shaker connected to the autoclave in which most industrial hydrothermal crystals are grown. The waveform can be modulated to induce transport of nutrient in a singular direction, customized to the topology of the apparatus. As it stands currently, the growth of most crystals that require autoclaves for their production can take anywhere from 3 months to up to 2 years, and accordingly carries many costs, particularly electricity and supervision of the autoclave(s), and other issues that may arise during the growth. While the product of this labor results in high-quality crystals, in reality, these are not at all what is needed outside of the laboratory environment. Using the assisted crystal hydrothermal growth process, average crystal growth can be cut in half, with the resulting crystals consequently being of a slightly lower quality, though still sufficient for most engineering purposes. Another advantage of using a piezoelectric shaker is that an additional sensor can be added to the autoclave to monitor the health of the autoclave using trending data obtained during the growth.

A crystal growth apparatus includes a pressure-resistant vessel; a plurality of support tables arranged inside the pressure-resistant vessel; inner vessels each placed over the support tables, respectively; growth vessels contained the inner vessels, respectively; a heating means for heating the growth vessels; and a central rotating shaft connected to the support tables. The central rotating shaft is distant from central axes of the inner vessels, respectively. A seed crystal, a raw material of the Group 13 element and a flux are charged in each of the growth vessels, and the growth vessels are heated to form a melt and a nitrogen-containing gas is supplied to the melt to grow a crystal of a nitride of said Group 13 element while the central rotating shaft is rotated.

A device substrate in which no streaked morphological abnormality occurs is achieved. A GaN template substrate includes: a base substrate; and a first GaN layer epitaxially formed on the base substrate, wherein the first GaN layer has a compressive stress greater than or equal to 260 MPa that is intrinsic in an inplane direction, or a full width at half maximum of a peak representing E2 phonons of GaN near a wavenumber of 568 cm.sup.1 in a Raman spectrum is lower than or equal to 1.8 cm.sup.1. With all of these requirements, a device substrate includes: a second GaN layer epitaxially formed on the first GaN layer; and a device layer epitaxially formed on the second GaN layer and made of a group 13 nitride.

A device substrate in which no streaked morphological abnormality occurs is achieved. A GaN template substrate includes: a base substrate; and a first GaN layer epitaxially formed on the base substrate, wherein the first GaN layer has a compressive stress greater than or equal to 260 MPa that is intrinsic in an inplane direction, or a full width at half maximum of a peak representing E2 phonons of GaN near a wavenumber of 568 cm.sup.1 in a Raman spectrum is lower than or equal to 1.8 cm.sup.1. With all of these requirements, a device substrate includes: a second GaN layer epitaxially formed on the first GaN layer; and a device layer epitaxially formed on the second GaN layer and made of a group 13 nitride.