Semiconductor device and method of its manufacture

A method of manufacturing a plurality of semiconductor devices, each of device principal-face surface area Sc predetermined by an at least 1 mm2 minimum size allowing the device to be functional, on a GaN device wafer screened from a plurality of vapor-phase grown GaN substrates to ensure a minimum 10% yield from the plurality of semiconductor devices, as defined by a minimum reverse breakdown voltage acceptable for the devices to be products, the method comprising:

• a step of producing a plurality of GaN substrates by an inversion-domain reducing vapor-phase growth process, the substrates each defining a principal face that is either the (0001) Ga face or a surface vicinally misoriented with respect to the (0001) Ga face;
• a step of testing the plurality of GaN substrates to screen for a minimum 10% device yield, said testing and screening step including
• a substep of characterizing inversion domains in the principal face of each of the plurality of GaN substrates by one technique selected from i) etching the substrates with a predetermined alkali solution for a predetermined time at a predetermined temperature, ii) cathodoluminescence, or iii) observation under a fluorescence microscope, and based on the inversion-domain characterization, determining, for each of the plurality of GaN substrates, the principal-face area St cm2 of the inversion domains collectively, finding the ratio St/ S, of St to the total area S cm2 of the substrate principal face, and selecting, as prepared GaN substrates from the plurality of GaN substrates, GaN substrates whose St/S is not greater than 0.5;
• a substep of determining the number of inversion domains of 1 μm2 or greater surface area in the principal face of the prepared GaN substrates, as D cm−2;
• and
• a substep of selecting those prepared GaN substrates whose product Sc×D is less than 2.3, as correlating to a device yield of at least 10% from semiconductor devices, each of said principal-face functional surface area Sc when grown on the substrates;
• a step of growing an at least single-lamina, device-forming semiconductor layer onto the principal face of the selected prepared GaN substrates;
• a step of dividing each of the selected prepared GaN substrates, on which the device-forming semiconductor layer has been grown into chips each of area Sc;
• a step of reverse-breakdown-voltage testing the device chips for the at least 10% whose reverse breakdown voltage is at or above the acceptable minimum.