  We completed a search for circumstellar disks around Herbig Be stars using
the NRAO Very Large Array (VLA) and the IRAM Plateau de Bure (PdB)
interferometers. We present our new VLA and PdBI data for the three objects MWC
297, Z CMa, and LKHa 215. We constructed the SED from near-IR to centimeter
wavelengths by adding our millimeter and centimeter data to the available data
at other wavelengths, mainly Spitzer images. The entire SED was fitted using a
disk+envelope model. In addition, we compiled all the disk millimeter
observations in the literature and completed a statistical analysis of all the
data. We show that the disk mass is usually only a small percentage (less than
10%) of the mass of the entire envelope in HBe stars. For the disks, there are
large source-to-source variations. Two disks in our sample, R Mon and Z CMa,
have similar sizes and masses to those found in T Tauri and Herbig Ae stars.
The disks around MWC 1080 and MWC 297 are, however, smaller (rout<100 AU). We
did not detect the disks towards MWC 137 and LkHa 215 at millimeter
wavelengths, which limits the mass and the size of the possible circumstellar
disks. A comparison between our data and previous results for T Tauri and
Herbig Ae stars indicates that although massive disks (0.1 Msun) are found in
young objects (10^4 yr), the masses of the disks around Herbig Be stars are
usually 5-10 times lower than those around lower mass stars. We propose that
disk photoevaporation is responsible for this behavior. In Herbig Be stars, the
UV radiation disperses the gas in the outer disk on a timescale of a few 10^5
yr. Once the outer part of the disk has vanished, the entire gaseous disk is
photoevaporated on a very short timescale (10^5 yr) and only a small, dusty
disk consisting of large grains remains.
