Pendeo epitaxial structures and devices

A method of making a microelectronic device structure, comprising:

• depositing an oxide layer on a substrate;
• depositing a photoresist layer on the oxide layer;
• patterning, exposing and developing the photoresist layer, and etching the oxide layer, to expose a surface of the substrate;
• etching the exposed surface of the substrate to form a trench cavity therein;
• depositing a patterned material supportive of a coalescent Pendeo layer thereon, on at least a portion of an inside surface of the trench cavity.

A method of forming a trench lateral epitaxial overgrowth substrate on a base member, comprising:

• depositing an oxide layer on the base member;
• depositing a photoresist layer on the oxide layer;
• patterning, exposing and developing the photoresist layer, and etching the oxide layer, to expose a surface of the base member;
• etching the exposed surface of the base member to form a trench cavity therein;
• depositing a patterned material supportive of a coalescent Pendeo layer thereon, on at least a portion of an inside surface of the trench cavity;
• and
• growing lateral epitaxial growth projections from side surfaces of the trench cavity toward and into contact with one another to form a bridged lateral overgrowth formation overlying the trench cavity above the patterned material on the floor of the trench cavity.

A method of making a microelectronic device assembly, comprising:

• forming a first coalesced Pendeo layer of GaN on a heteroepitaxial substrate;
• growing a layer of GaN on the coalesced Pendeo layer, by MOCVD;
• growing a layer of GaN on the MOCVD layer of GaN, by HVPE;
• forming a second coalesced Pendeo layer of GaN, on the HVPE layer of GaN;
• growing a layer of GaN on the second coalesced Pendeo layer of GaN, by MOCVD;
• and
• forming a microelectronic device structure on and/or in the MOCVD layer of GaN on the second coalesced Pendeo layer of GaN.

A microelectronic device assembly, comprising:

• a first Pendeo layer of GaN;
• a first MOCVD layer of GaN on the first Pendeo layer of GaN;
• an HVPE layer of GaN on the first MOCVD layer of GaN;
• a second Pendeo layer of GaN on the HVPE layer of GaN;
• a second MOCVD layer of GaN on the second Pendeo layer of GaN;
• and
• a microelectronic device structure on and/or in the second MOCVD layer of GaN.

A microelectronic device assembly, comprising:

• a sapphire substrate;
• GaN pedestals on said sapphire substrate, defining a trench cavity, wherein the sapphire substrate constitutes a floor portion of the trench cavity, and includes convex shoulders adjacent to the GaN pedestals;
• and
• a growth-blocking layer on said convex shoulders, whereby said growth-blocking layer suppresses vertical and angular growth from said convex shoulders, to accommodate lateral epitaxial overgrowth across the trench cavity above said convex shoulders.