Methods of forming a semiconductor device can include forming a semiconductor structure on a substrate, the semiconductor structure having mesa sidewalls and a mesa surface opposite the substrate. A contact layer can be formed on the mesa surface wherein the contact layer has sidewalls and a contact surface opposite the mesa surface and wherein the contact layer extends across substantially an entirety of the mesa surface. A passivation layer can be formed on the mesa sidewalls and on portions of the contact layer sidewalls adjacent the mesa surface, and the passivation layer can expose substantially an entirety of the contact surface of the contact layer. Related devices are also discussed.