A new type of thermally stable GaAs/AlGaAs tunnel diode with an intermediate i-layer is proposed as a connecting element between photoactive sub-elements in monolithic multijunction photoconverters. In the temperature range of (25–80) °C, the current-voltage characteristics for two types of n++-GaAs(δSi)/p++-Al0.4Ga0.6As(C) and n++-GaAs(δSi)/i-GaAs/ p++-Al0.4Ga0.6As:(C) structures of connecting tunnel diodes were studied. The temperature dependences of the peak tunneling current density – (Jp) and differential resistance – (Rd) were obtained. In the samples of tunnel diodes of the structure with an i-layer, an order of magnitude higher Jp values and an order of magnitude lower Rd values were obtained, with higher temperature stability than in the samples of the structure without an i-layer. The results obtained are useful in the development and creation of monolithic multijunction photoconverters of high-power laser radiation.