Although the ultra-wide bandgap (UWBG) semiconductor aluminum nitride (AlN) has been routinely used in optoelectronics such as deep ultraviolet (DUV) light emitting diodes (LEDs) and lasers, its adoption in RF and power electronics remains largely unexplored. This dissertation demonstrates the significant potential of AlN platform for the next generation electronics to merge logic, memory and RF communication, the three pillars of electronic information systems. Built upon structurally-pure single crystal AlN substrates with high thermal conductivity, the high and best-balanced performances of p-channel and n-channel devices presented in this dissertation challenge the common misconception that high performance complementary logic is impossible with nitride semiconductors. Together with the radio frequency (RF) filters that have already been demonstrated on the same platform thanks to the high piezoelectricity of AlN, the results in this dissertation are expected to enable a fully-integrated monolithic RF signal processing solution on AlN. In this dissertation, utilizing polarization engineering, conductive channels are generated on the electrically-insulating AlN by adding a thin layer of GaN or AlGaN on top. Taking advantage of the capability to maintain sharp heterointerfaces by molecular beam epitaxy (MBE), combined with the state-of-the-art fabrication process, devices with record performances were achieved. First, the observation and properties of polarization-induced 2d hole gases (2DHGs) in GaN/AlN heterostructures on metal-polar single crystal AlN substrates are presented. The reduced dislocation densities on single crystal AlN substrates compared to foreign substrates such as SiC and sapphire improve hole mobility, and a record high hole mobility of ∼ 280 cm2/V·s is measured at 10 K. By leveraging the highly-conductive 2DHG in conjunction with a highly-scaled 3D-gating architecture, the fastest (fT/fMAX = 25/45 GHz) p-channel FinHFETs that deliver record-high on-currents(ION =1.3A/mm at room temperature) and >0.5 W/mm at 6 GHz RF output power are achieved. This is the first time RF output power has been obtained in nitride pFETs, marking the entrance of nitride transistor technology into the new frontier of RF CMOS. Next, by flipping the polarity of the structure, 2d electron gases (2DEGs) can be induced in N-polar GaN/AlN heterostructures. Unlike metal-polar AlN, the homoepitaxy of N-polar AlN is challenging, primarily due to the high reactivity of N-polar AlN surface. A new atomic surface cleaning technique— Al-assisted surface cleaning is developed and enables MBE homoepitaxy of electronic- and optical-grade N-polar AlN. 2DEGs are successfully observed in N-polar GaN/AlGaN heterostructures with sheet resistances of ∼300 Ω/□. These are among the lowest sheet resistances reported in III-nitride 2DEGs. The first N-polar HEMTs on AlN are enabled by these 2DEGs, showing a high on-current of 2.6 A/mm, a high speed (fT/fMAX = 68/100 GHz) as well as >3 W/mm RF output power at 6 GHz. While there is large room for future improvement, these exciting performances already demonstrated in the first generation devices mark important milestones towards highly reliable RF electronics with excellent thermal management based on N-polar AlN HEMTs. Finally, as an important first step towards direct integration of magnetic memory on the same nitride semiconductor platform, the MBE growth of ferrimagnetic Mn4N hosting desirable properties for spintronic applications is explored on GaN to form a all-nitride ferrimagnet/semiconductor heterostructure. Through exploration of nucleation and growth conditions, the MBE growth condition for c-axis aligned Mn4N on GaN with smooth surface morphologies is uncovered. Instead of direct nucleation of Mn4N on GaN substrates, a homoepitaxial GaN buffer layer is found to be helpful for improving the quality and surface morphology of the Mn4N epilayer. The ferrimagnetism evidenced by the clear anomalous Hall hysteresis loops at room temperature, along with the smooth surface morphology of Mn4N on GaN, lay the groundwork for bringing magnetic memory onto the AlN platform. As an aside, because of the rich magnetic phases within the Mn-N system and the large potential of antiferromagnetic materials for future spintronics, the magnetic properties of antiferromagnetic MnN are studied using optical second harmonic generation (SHG). The point group symmetry of MBE grown antiferromagnetic MnN films is identified as 2/m1’ and a loose upper bound on the domain sizes of 0.65 μm is placed. These results demonstrate the effectiveness of SHG for detecting the Neel order in metallic antiferromagnets and are expected to contribute to the recent efforts in using antiferromagnets for spintronic applications. With the results presented in this dissertation, the vision of fully-integrated electronics capable of logic, memory and RF communication functionalities on the single crystal AlN platform is very close to being realized, and will hopefully be greater than the sum of its parts.