Power transistor with soft recovery body diode

A transistor comprising:

• a silicon carbide substrate having a first doping type and a first doping concentration;
• a silicon carbide drift layer on the silicon carbide substrate, the drift layer having the first doping type and a second doping concentration;
• a junction implant in the drift layer opposite the silicon carbide substrate, the junction implant comprising:
• a body well having a second doping type opposite the first doping type;
• and
• a source well having the first doping type, wherein the source well is within the body well;
• a source contact in electrical contact with the source well and the body well;
• a drain contact in electrical contact with the silicon carbide substrate;
• a gate insulator on the drift layer and over a portion of the body well and the source well;
• a gate contact on the gate insulator;
• and
• a recombination region below the body well,
• wherein a softness factor of a body diode between the source contact and the drain contact is greater than 0.5,
• wherein the body diode is a non-punch through diode,
• wherein the recombination region has a first concentration of recombination centers and the drift layer has a second concentration of recombination centers, and
• wherein the first concentration of recombination centers is between 5 and 10 times greater than a the second concentration of recombination centers.

A transistor comprising:

• a substrate having a first doping type and a first doping concentration;
• a drift layer on the substrate, the drift layer having the first doping type and a second doping concentration;
• a junction implant in the drift layer opposite the substrate, the junction implant comprising:
• a body well having a second doping type opposite the first doping type;
• and
• a source well having the first doping type, wherein the source well is within the body well;
• a source contact in electrical contact with the source well and the body well;
• a drain contact in electrical contact with the substrate;
• a gate insulator on the drift layer and over a portion of the body well and the source well;
• a gate contact on the gate insulator;
• and
• a body diode between the source contact and the drain contact,
• wherein the body diode is configured to have a first concentration of minority carriers at an interface between the body well and the drift layer that is less than a second concentration of minority carriers at an interface between the drift layer and the substrate during forward bias operation.

A method for manufacturing a transistor comprising:

• providing a substrate having a first doping type and a first doping concentration;
• providing a drift layer on the substrate, the drift layer having the first doping type and a second doping concentration;
• providing a junction implant in the drift layer opposite the substrate, the junction implant comprising:
• providing a body well having a second doping type opposite the first doping type and a third doping concentration;
• providing a source well having the first doping type, wherein the source well is within the body well;
• depositing a source contact in electrical contact with the source well and the body well;
• depositing a drain contact in electrical contact with the substrate;
• providing a gate insulator on the drift layer and over a portion of the body well and the source well;
• depositing a gate contact on the gate insulator;
• and
• providing a body diode between the source contact and the drain contact,
• wherein a thickness of the drift layer and the second and third doping concentrations are configured so that a depletion region formed in the body diode when the body diode is biased at a breakdown voltage of the body diode does not extend into the substrate.

A transistor comprising:

• a substrate having a first doping type and a first doping concentration;
• a drift layer on the substrate, the drift layer having the first doping type and a second doping concentration;
• a junction implant in the drift layer opposite the substrate, the junction implant comprising:
• a body well having a second doping type opposite the first doping type;
• and
• a source well having the first doping type, wherein the source well is within the body well;
• a source contact in electrical contact with the source well and the body well;
• a drain contact in electrical contact with the substrate;
• a gate insulator on the drift layer and over a portion of the body well and the source well;
• and
• a body diode between the source contact and the drain contact;
• and
• a gate contact on the gate insulator,
• wherein the body diode is a non-punch through diode.