Not sure why you're being downvoted, because this is absolutely the case. Examples include L4, QNX, FreeRTOS, Minix, etc. The vast majority of kernels that have been designed specifically for embedded or real-time applications are microkernels.
That, of course, doesn't mean that only microkernels are used in embedded and real-time applications. It's not uncommon to see, for example, a stripped-down Linux or even Windows in some applications. In some cases, even MS-DOS and its kin are still used. But by and large, the most of the kernels you're looking at in this space are indeed microkernels.
The microkernel architecture also offers some advantages in the high-assurance space. See seL4, for example. This doesn't necessarily have anything to do with any technological superiority of microkernels, per se, but they tend to be far smaller than monolithic kernels, which in turn makes them much easier to audit and verify. The Minix 3 kernel, for example, is something like 6,000 lines of C -- roughly 2/3 the size of GNU grep -- which makes it comparatively easy to audit, simply because there's less code to audit.
That, of course, doesn't mean that only microkernels are used in embedded and real-time applications. It's not uncommon to see, for example, a stripped-down Linux or even Windows in some applications. In some cases, even MS-DOS and its kin are still used. But by and large, the most of the kernels you're looking at in this space are indeed microkernels.
The microkernel architecture also offers some advantages in the high-assurance space. See seL4, for example. This doesn't necessarily have anything to do with any technological superiority of microkernels, per se, but they tend to be far smaller than monolithic kernels, which in turn makes them much easier to audit and verify. The Minix 3 kernel, for example, is something like 6,000 lines of C -- roughly 2/3 the size of GNU grep -- which makes it comparatively easy to audit, simply because there's less code to audit.