This work details the analysis and design of compact square-law envelope detectors employing Schottky diodes for use as low-power energy efficient Gbps on-off-keying receivers. An efficiency and noise model is presented and verified, and the implications for system design are discussed. The main motivation for these receivers and models is for the design of low-cost, low-complexity millimeter wave MIMO systems. Both antenna-coupled and probed detectors are designed and measured. A detector with record minimum NEP of 0.28 pW/√Hz is presented. A high input impedance peaking baseband LNA for wideband buffering of the diode baseband output is designed, fabricated, and integrated with the detector to create an on-off-keying receiver with a bit rate of 1 Gbps. The receiver exhibits a sensitivity of -36 dBm for a bit error ratio of 1E-3, which is a record for Gbps nonpreamplified on-off-keying receivers employing passive detectors. The receiver energy efficiency is 1.44 pJ/bit, which is competitive with even monolithic implementations. It also dissipates a low absolute power of only 1.15 mW, which is especially attractive for multi-antenna systems. This thesis demonstrates that nonlinear, nonstandard detector-based receivers can simultaneously achieve both high data rate and low power consumption over the air in a commercial millimeter wave band.