The presence of a minimal length has a significant effect on relativistic
physical systems. This paper discusses how minimal length affects the efficiency of a
relativistic quantum heat engine. The working substance chosen is a Dirac particle
trapped in a one-dimensional infinite potential well. In this paper, we calculate
the efficiency of a quantum heat engine in three thermodynamic cycles, namely the
Carnot, Otto, and Brayton cycles. The engine efficiency is calculated analytically
and numerically. In this research, the minimal length is a correction factor for the
relativistic energy. The result is that the minimal length could increase or decrease
the efficiency of the relativistic quantum heat engine on the small potential width
according to the particle mass, the expansion parameter, and the thermodynamic
cycle.