Methods of fabricating aluminum gallium nitride/gallium nitride high electron mobility transistors having a gate contact on a gallium nitride based cap segment

A method of fabricating a high electron mobility transistor (HEMT), comprising:

• forming a first gallium nitride (GaN) layer on a substrate;
• forming an aluminum gallium nitride (AlGaN) layer on the first GaN layer;
• forming a GaN-based segment on the AlGaN layer, the GaN-based segment having an aluminum concentration of less than the AlGaN layer;
• forming a first ohmic contact to the AlGaN layer adjacent and spaced apart from the GaN segment to provide a source electrode;
• forming a second ohmic contact to the AlGaN layer adjacent and spaced apart from the GaN segment and opposite first ohmic contact such that the GaN segment is disposed between the first ohmic contact and the second ohmic contact to provide a drain electrode;
• and
• forming a non-ohmic contact on the GaN segment to provide a gate contact, the gate contact having a first sidewall which is substantially aligned with the a first sidewall of the GaN segment adjacent the source contact and the gate contact extending only a portion of a distance between the first sidewall the second ohmic contact.

A high electron mobility transistor (HEMT), comprising:

• a gallium nitride (GaN) channel layer;
• an aluminum gallium nitride (AlGaN) barrier layer;
• ohmic contacts on the AIGaN barrier layer to provide source and drain contacts;
• a non-ohmic gate contact disposed between the source and drain contacts;
• and
• means, operably associated with the non-ohmic gate contact and the AlGaN barrier layer, for reducing a resistance of the ohmic contacts and increasing a blocking voltage of the gate contact as compared to a device without the means for reducing a resistance of the ohmic contacts and increasing a blocking voltage of the gate contact.