Three-dimensional memory device including germanium-containing vertical channels and method of making the same

A three-dimensional memory device, comprising:

• an alternating stack of insulating layers and electrically conductive layers located over a substrate;
• a memory stack structure extending through the alternating stack, wherein the memory stack structure comprises a memory film and a vertical semiconductor channel contacting an inner sidewall of the memory film and comprising germanium at an atomic concentration greater than 50%;
• and
• a semiconductor oxide core laterally surrounded by the vertical semiconductor channel, wherein the semiconductor oxide core comprises a silicon-germanium oxide material having a radial concentration gradient of atomic concentration of silicon.

A three-dimensional memory device, comprising:

• an alternating stack of insulating layers and electrically conductive layers located over a substrate;
• a memory stack structure extending through the alternating stack, wherein the memory stack structure comprises a memory film and a vertical semiconductor channel contacting an inner sidewall of the memory film and comprising germanium at an atomic concentration greater than 50%;
• and
• a silicon-germanium alloy region located below the memory film, wherein the silicon-germanium alloy region has a vertical germanium concentration gradient such that a germanium concentration increases with a vertical distance from an interface with the memory film.