We discuss the properties of AlGaN / GaN superlattice (SL) related to the feasibility of a terahertz-range oscillator. The distortion of the conduction-band profile by the polarization fields has been taken into account. We have calculated the conduction-band offset between the pseudomorphic AlGaN barrier and the GaN quantum well, the first miniband width and energy dispersion, as functions of Al content in the barrier. As the short-period SL miniband energy dispersion contains contributions from next to nearest neighbors, it causes anharmonic electron oscillations at the multiples of the fundamental Bloch frequency. The Al content and SL period that favor high-frequency oscillations have been determined.Negative differential conductivity (NDC) in semiconductor superlattices (SLs) 1 is at the origin of various proposals for compact submillimeter wave sources. The NDC in dc-biased SLs results in traveling electrical domain formation that has been used in a 147 GHz microwave source made of the InGaAs/ GaAs SL. 2,3 Another type of SL source, the Bloch oscillator, 1 is projected to oscillate at the Bloch frequency (terahertz region) and exploits the existence of high-frequency NDC. At the moment, no live example of the Bloch-type source exists because the NDC at zero frequency induces electric-field domains, thus preventing electrons from oscillating at the Bloch frequency. 4,5 Operation of the SL source relies on carrier dynamics specific to a narrow conduction band. High-frequency and zero-frequency NDC may or may not appear simultaneously depending on details of the miniband electron energy dispersion. If the dispersion is not of simple cosine-type, it is possible to arrange the high-frequency NDC while suppressing the dc instability. This prevents electrical domain formation and allows Bloch oscillations.The output power of the source depends on the current and voltage swing in the NDC region. Basically, it would be beneficial to high-power device operation if the SL structure was made of a wide band-gap semiconductor. Thus, the GaN / AlGaN SL is a possible candidate for high-power submillimeter wave source. GaN-based electronic devices can sustain higher voltage and are less sensitive to the high dislocation density as compared to narrow-gap GaAs-InAsbased devices.In this letter, we discuss the properties of an AlGaN / GaN SL relevant to microwave source feasibility. The wurtzite ͑0001͒AlGaN / GaN SL is the intrinsic Stark SL where the polarization fields shift the energy levels of confined electrons. Proper design of a GaN / AlGaN SL source should account for intrinsic electric fields. Polarization fields in a SL stem from the spontaneous polarization in the bulk and lattice-mismatch-induced piezoelectric component. We calculate the electron energy dispersion and width of the first miniband in the intrinsic Stark GaN-based SL and discuss the results related to feasibility of a submillimeter wave source.The dynamic properties of the SL depend on the conduction-band profile as determined by the conductionband off...

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