Method for forming a film with a graded bandgap by deposition of an amorphous material from a plasma

A method of forming a film of an amorphous material on a substrate by deposition of a plasma, the method comprising the steps of:

• placing the substrate in an enclosure,
• continuously introducing into the enclosure a film precursor gas at a flow rate, the film precursor gas containing one component or multiple components,
• extracting unreacted and dissociated gas from the enclosure so as to provide a low pressure in the enclosure,
• introducing microwave energy into the gas within the enclosure to produce a plasma therein by distributed electron cyclotron resonance (DECR) and cause the material to be deposited from the plasma on the substrate,
• wherein the said flow rate is altered during the course of deposition of material without varying the composition of the gas introduced into the enclosure, so as to cause the bandgap to vary over the thickness of the deposited material and a plurality of layers are successively deposited on the substrate, each layer having a larger bandgap than the previous layer.

A method of forming a film of an amorphous material on a substrate by deposition of a plasma, the method comprising the steps of:

• placing the substrate in an enclosure,
• continuously introducing into the enclosure a film precursor gas at a flow rate, the film precursor gas containing one component or multiple components,
• extracting unreacted and dissociated gas from the enclosure so as to provide a low pressure in the enclosure,
• introducing microwave energy into the gas within the enclosure to produce a plasma therein by distributed electron cyclotron resonance (DECR) and cause the material to be deposited from the plasma on the substrate,
• wherein the said flow rate is altered during the course of deposition of material without varying the composition of the gas introduced into the enclosure, so as to cause the bandgap to vary over the thickness of the deposited material and a plurality of layers are successively deposited on the substrate, each layer having a smaller bandgap than the previous layer.

A method of forming a film of an amorphous material on a substrate by deposition of a plasma, the method comprising the steps of:

• placing the substrate in an enclosure,
• continuously introducing into the enclosure a film precursor gas at a flow rate, the film precursor gas containing one component or multiple components,
• extracting unreacted and dissociated gas from the enclosure so as to provide a low pressure in the enclosure,
• introducing microwave energy into the gas within the enclosure to produce a plasma therein by distributed electron cyclotron resonance (DECR) and cause the material to be deposited from the plasma on the substrate,
• wherein the said flow rate is altered during the course of deposition of material without varying the composition of the gas introduced into the enclosure, so as to cause the bandgap to vary over the thickness of the deposited material and the layers are deposited so as to cause the bandgap to have a minimum at a point spaced from both the first and last layers to be deposited.