Growth of germanium epitaxial thin film with negative photoconductance characteristics and photodiode using the same
View Patent ↗A method of growing a germanium (Ge) epitaxial thin film having negative photoconductance characteristics and a photodiode using the same are provided. The method of growing the germanium (Ge) epitaxial thin film includes growing a germanium (Ge) thin film on a silicon substrate at a low temperature, raising the temperature to grow the germanium (Ge) thin film, and growing the germanium (Ge) thin film at a high temperature, wherein each stage of growth is performed using reduced pressure chemical vapor deposition (RPCVD). The three-stage growth method enables formation of a germanium (Ge) epitaxial thin film characterized by alleviated stress on a substrate, a lowered penetrating dislocation density, and reduced surface roughness.
1. A method of growing a germanium (Ge) epitaxial thin film, comprising:
growing a first germanium (Ge) thin film on a silicon substrate at a low temperature;
growing a second germanium (Ge) thin film while raising the temperature; and
growing a third germanium (Ge) thin film at a high temperature,
wherein each growing is performed using reduced pressure chemical vapor deposition (RPCVD), and the first, second and third germanium (Ge) thin films grown by the above steps have negative photoconductance characteristics.
2. The method of claim 1 , wherein the growing of the first germanium (Ge) thin film at a low temperature is performed at a deposition temperature of about 350 to about 450° C. under a pressure of about 10 to about 90 Torr to grow the thin film to a thickness of about 80 to about 120 nm.
3. The method of claim 1 , wherein the growing of the second germanium (Ge) thin film while raising the temperature is performed on the first germanium (Ge) thin film by raising a temperature from about 350 to about 450° C. to about 600 to about 700° C. at a rate of about 5 to about 15° C. per minute to grow the second thin film to a thickness of about 180 to about 220 nm.
4. The method of claim 1 , wherein the growing of the third germanium (Ge) thin film at a high temperature is performed on the second germanium (Ge) thin film at a deposition temperature of about 600 to about 700° C. under a pressure of about 10 to about 90 Torr.
5. The method of claim 1 , wherein a deposition rate in raising the temperature to grow the second germanium (Ge) thin film is the same as that in growing the first germanium (Ge) thin film at a low temperature, and a deposition rate in growing the third germanium (Ge) thin film at a high temperature is at least twice that in growing the first germanium (Ge) thin film at a low temperature.
6. A method of growing a germanium (Ge) epitaxial thin film, comprising:
growing a low-temperature germanium (Ge) thin film on a silicon substrate at a first temperature;
growing a rising-temperature germanium (Ge) thin film on the low-temperature germanium (Ge) thin film under temperature that continuously changes from the first temperature to a second temperature higher than the first temperature; and
growing a high-temperature germanium (Ge) thin film on the rising-temperature germanium (Ge) thin film at the second temperature.