Photodetector, photoelectric sensor, methods of forming the same and determining concentration

A photoelectric sensor comprising:

• one or more photodetectors, each of the one or more photodetectors comprising:
• a semiconductor substrate;
• an aluminium nitride (AlN) layer on the semiconductor substrate;
• one or more aluminium gallium nitride (AlGaN) layers over the aluminium nitride (AlN) layer;
• a doped gallium nitride (GaN) layer over the one or more aluminium gallium nitride (AlGaN) layers;
• a first mesa structure on a first portion of the doped gallium nitride (GaN) layer;
• and
• a second mesa structure spaced from the first mesa structure and on a second portion of the doped gallium nitride (GaN) layer;
• wherein the first mesa structure comprises:
• a first undoped gallium nitride (GaN) layer on the doped gallium nitride (GaN) layer;
• and
• a first aluminium gallium nitride (AlGaN) layer on the first undoped gallium nitride (GaN) layer;
• wherein the second mesa structure comprises:
• a second undoped gallium nitride (GaN) layer on the doped gallium nitride (GaN) layer;
• and
• a second aluminium gallium nitride (AlGaN) layer on the second undoped gallium nitride (GaN) layer;
• and
• wherein the photodetector further comprises:
• a first electrode over the first mesa structure;
• and
• a second electrode over the second mesa structure;
• an electrically insulating layer over the one or more photodetectors;
• and
• a holder on the electrical insulating layer, the holder configured to hold a sample.

A method of forming a photodetector, the method comprising:

• forming an aluminium nitride (AlN) layer on a semiconductor substrate;
• forming one or more aluminium gallium nitride (AlGaN) layers over the aluminium nitride (AlN) layer;
• forming a doped gallium nitride (GaN) layer over the one or more aluminium gallium nitride (AlGaN) layers;
• forming a first mesa structure on a first portion of the doped gallium nitride (GaN) layer;
• and
• forming a second mesa structure spaced from the first mesa structure and on a second portion of the doped gallium nitride (GaN) layer;
• wherein the first mesa structure comprises:
• a first undoped gallium nitride (GaN) layer on the doped gallium nitride (GaN) layer;
• and
• a first aluminium gallium nitride (AlGaN) layer on the first undoped gallium nitride (GaN) layer;
• and
• wherein the second mesa structure comprises:
• a second undoped gallium nitride (GaN) layer on the doped gallium nitride (GaN) layer;
• and
• a second aluminium gallium nitride (AlGaN) layer on the second undoped gallium nitride (GaN) layer;
• and
• wherein the method further comprises:
• forming a first electrode over the first mesa structure;
• and
• forming a second electrode over the second mesa structure.

A method of forming a photoelectric sensor, the method comprising:

• forming an electrical insulating layer over one or more photodetectors, each of the one or more photodetectors comprising:
• a semiconductor substrate;
• an aluminium nitride (AlN) layer on the semiconductor substrate;
• one or more aluminium gallium nitride (AlGaN) layers over the aluminium nitride (AlN) layer;
• a doped gallium nitride (GaN) layer over the one or more aluminium gallium nitride (AlGaN) layers;
• a first mesa structure on a first portion of the doped gallium nitride (GaN) layer;
• and
• a second mesa structure spaced from the first mesa structure and on a second portion of the doped gallium nitride (GaN) layer;
• wherein the first mesa structure comprises:
• a first undoped gallium nitride (GaN) layer on the doped gallium nitride (GaN) layer;
• and
• a first aluminium gallium nitride (AlGaN) layer on the first undoped gallium nitride (GaN) layer;
• wherein the second mesa structure comprises:
• a second undoped gallium nitride (GaN) layer on the doped gallium nitride (GaN) layer;
• and
• a second aluminium gallium nitride (AlGaN) layer on the second undoped gallium nitride (GaN) layer;
• and
• wherein the photodetector further comprises:
• a first electrode over the first mesa structure;
• and
• a second electrode over the second mesa structure;
• and
• forming a holder on the dielectric layer, the holder configured to hold a sample.

A method of determining a concentration of a substance in a sample, the method comprising:

• providing the sample into a photoelectric sensor, the photoelectric sensor comprising:
• one or more photodetectors, each of the one or more photodetectors comprising:
• a semiconductor substrate;
• an aluminium nitride (AlN) layer on the semiconductor substrate;
• one or more aluminium gallium nitride (AlGaN) layers over the aluminium nitride (AlN) layer;
• a doped gallium nitride (GaN) layer over the one or more aluminium gallium nitride (AlGaN) layers;
• a first mesa structure on a first portion of the doped gallium nitride (GaN) layer;
• and
• a second mesa structure spaced from the first mesa structure and on a second portion of the doped gallium nitride (GaN) layer;
• wherein the first mesa structure comprises:
• a first undoped gallium nitride (GaN) layer on the doped gallium nitride (GaN) layer;
• and
• a first aluminium gallium nitride (AlGaN) layer on the first undoped gallium nitride (GaN) layer;
• wherein the second mesa structure comprises:
• a second undoped gallium nitride (GaN) layer on the doped gallium nitride (GaN) layer;
• and
• a second aluminium gallium nitride (AlGaN) layer on the second undoped gallium nitride (GaN) layer;
• and
• wherein the photodetector further comprises:
• a first electrode over the first mesa structure;
• and
• a second electrode over the second mesa structure;
• an electrically insulating layer over the one or more photodetectors;
• and
• a holder on the electrical insulating layer, the holder configured to hold a sample;
• illuminating the sample with an ultraviolet light;
• determining a photocurrent from the one or more photodetectors in response to the ultraviolet light passing through the sample;
• and
• determining a concentration of the substance based on the photocurrent.