High electron mobility transistors having improved contact spacing and/or improved contact vias

A high electron mobility transistor (HEMT), comprising:

• a substrate;
• a semiconductor structure on the substrate;
• a first via and a second via, each extending in the substrate and the semiconductor structure;
• a first ohmic source contact on the first via and a second ohmic source contact on the second via;
• a drain contact on the semiconductor structure and between, in plan view, the first via and the second via;
• and
• a gate contact between the first ohmic source contact and the drain contact, wherein a width of the first via decreases as the first via extends from a bottom surface of the substrate to a top surface of the substrate.

A high electron mobility transistor (HEMT), comprising:

• a substrate;
• a semiconductor structure on the substrate;
• a first ohmic source contact and a second ohmic source contact on the semiconductor structure;
• a drain contact on the semiconductor structure between the first ohmic source contact and the second ohmic source contact;
• and
• a via extending between a bottom surface of the substrate and the first ohmic source contact,
• wherein a distance between the first ohmic source contact and the second ohmic source contact is 60 μm or less, and
• wherein the via is located below a first portion of the first ohmic source contact, and wherein a second portion of the drain contact is between the first portion of the first ohmic source contact and the second ohmic source contact.