A study of the quasistatic hybrid mode in high‐electron‐mobility semiconductor plasmas subject to perpendicular static electric and magnetic fields shows that when carrier‐heating effects are fully taken into account an entirely new mode arises as a result of the carrier heating. This mode has properties suitable for readily generating the two‐stream instability and the interaction of this mode with hole‐cyclotron harmonics is much stronger than that of any unheated mode.