We report the transverse mode characteristics of InGaAs-GaAs vertical-cavity surface-emitting lasers (VCSEL's) buried in a low-temperature-deposited amorphous GaAs (a-GaAs) layer. The maximum current maintaining a stable fundamental transverse mode is increased by the antiguide effect of the a-GaAs clad with a high refractive index, For 10- and 15-mu m-diameter devices, we attain a stable single-mode emission over a wide range of current, The antiguide effects and transverse mode profiles in vertical cavity lasers buried in the high refractive index clad are calculated using a two-dimensional beam propagation method.